/**********************************************************************

  proc.c - Proc, Binding, Env

  $Author$
  created at: Wed Jan 17 12:13:14 2007

  Copyright (C) 2004-2007 Koichi Sasada

**********************************************************************/

#include "eval_intern.h"
#include "internal.h"
#include "gc.h"
#include "iseq.h"

/* Proc.new with no block will raise an exception in the future
 * versions */
#define PROC_NEW_REQUIRES_BLOCK 0

const rb_cref_t *rb_vm_cref_in_context(VALUE self, VALUE cbase);

struct METHOD {
    const VALUE recv;
    const VALUE klass;
    const rb_method_entry_t * const me;
    /* for bound methods, `me' should be rb_callable_method_entry_t * */
};

VALUE rb_cUnboundMethod;
VALUE rb_cMethod;
VALUE rb_cBinding;
VALUE rb_cProc;

static VALUE bmcall(VALUE, VALUE, int, VALUE *, VALUE);
static int method_arity(VALUE);
static int method_min_max_arity(VALUE, int *max);

#define attached id__attached__

/* Proc */

#define IS_METHOD_PROC_IFUNC(ifunc) ((ifunc)->func == bmcall)
#define IS_METHOD_PROC_ISEQ(iseq) \
    (RUBY_VM_IFUNC_P(iseq) && \
     IS_METHOD_PROC_IFUNC((struct vm_ifunc *)(iseq)))

static void
proc_mark(void *ptr)
{
    rb_proc_t *proc = ptr;
    RUBY_MARK_UNLESS_NULL(proc->block.proc);
    RUBY_MARK_UNLESS_NULL(proc->block.self);
    if (proc->block.ep) {
	RUBY_MARK_UNLESS_NULL(rb_vm_proc_envval(proc));
    }
    if (proc->block.iseq && RUBY_VM_IFUNC_P(proc->block.iseq)) {
	rb_gc_mark((VALUE)(proc->block.iseq));
    }
    RUBY_MARK_LEAVE("proc");
}

typedef struct {
    rb_proc_t basic;
    VALUE env[3]; /* me, specval, envval */
} cfunc_proc_t;

static size_t
proc_memsize(const void *ptr)
{
    const rb_proc_t *proc = ptr;
    if (proc->block.ep == ((const cfunc_proc_t *)ptr)->env+1)
	return sizeof(cfunc_proc_t);
    return sizeof(rb_proc_t);
}

static const rb_data_type_t proc_data_type = {
    "proc",
    {
	proc_mark,
	RUBY_TYPED_DEFAULT_FREE,
	proc_memsize,
    },
    0, 0, RUBY_TYPED_FREE_IMMEDIATELY
};

VALUE
rb_proc_alloc(VALUE klass)
{
    rb_proc_t *proc;
    return TypedData_Make_Struct(klass, rb_proc_t, &proc_data_type, proc);
}

VALUE
rb_obj_is_proc(VALUE proc)
{
    if (rb_typeddata_is_kind_of(proc, &proc_data_type)) {
	return Qtrue;
    }
    else {
	return Qfalse;
    }
}

/* :nodoc: */
static VALUE
proc_dup(VALUE self)
{
    VALUE procval;
    rb_proc_t *src;
    rb_proc_t *dst;

    GetProcPtr(self, src);
    procval = rb_proc_alloc(rb_cProc);
    GetProcPtr(procval, dst);
    *dst = *src;
    dst->block.proc = procval;
    RB_GC_GUARD(self); /* for: body = proc_dup(body) */

    return procval;
}

/* :nodoc: */
static VALUE
proc_clone(VALUE self)
{
    VALUE procval = proc_dup(self);
    CLONESETUP(procval, self);
    return procval;
}

/*
 * call-seq:
 *   prc.lambda? -> true or false
 *
 * Returns +true+ for a Proc object for which argument handling is rigid.
 * Such procs are typically generated by +lambda+.
 *
 * A Proc object generated by +proc+ ignores extra arguments.
 *
 *   proc {|a,b| [a,b] }.call(1,2,3)    #=> [1,2]
 *
 * It provides +nil+ for missing arguments.
 *
 *   proc {|a,b| [a,b] }.call(1)        #=> [1,nil]
 *
 * It expands a single array argument.
 *
 *   proc {|a,b| [a,b] }.call([1,2])    #=> [1,2]
 *
 * A Proc object generated by +lambda+ doesn't have such tricks.
 *
 *   lambda {|a,b| [a,b] }.call(1,2,3)  #=> ArgumentError
 *   lambda {|a,b| [a,b] }.call(1)      #=> ArgumentError
 *   lambda {|a,b| [a,b] }.call([1,2])  #=> ArgumentError
 *
 * Proc#lambda? is a predicate for the tricks.
 * It returns +true+ if no tricks apply.
 *
 *   lambda {}.lambda?            #=> true
 *   proc {}.lambda?              #=> false
 *
 * Proc.new is the same as +proc+.
 *
 *   Proc.new {}.lambda?          #=> false
 *
 * +lambda+, +proc+ and Proc.new preserve the tricks of
 * a Proc object given by <code>&</code> argument.
 *
 *   lambda(&lambda {}).lambda?   #=> true
 *   proc(&lambda {}).lambda?     #=> true
 *   Proc.new(&lambda {}).lambda? #=> true
 *
 *   lambda(&proc {}).lambda?     #=> false
 *   proc(&proc {}).lambda?       #=> false
 *   Proc.new(&proc {}).lambda?   #=> false
 *
 * A Proc object generated by <code>&</code> argument has the tricks
 *
 *   def n(&b) b.lambda? end
 *   n {}                         #=> false
 *
 * The <code>&</code> argument preserves the tricks if a Proc object
 * is given by <code>&</code> argument.
 *
 *   n(&lambda {})                #=> true
 *   n(&proc {})                  #=> false
 *   n(&Proc.new {})              #=> false
 *
 * A Proc object converted from a method has no tricks.
 *
 *   def m() end
 *   method(:m).to_proc.lambda?   #=> true
 *
 *   n(&method(:m))               #=> true
 *   n(&method(:m).to_proc)       #=> true
 *
 * +define_method+ is treated the same as method definition.
 * The defined method has no tricks.
 *
 *   class C
 *     define_method(:d) {}
 *   end
 *   C.new.d(1,2)       #=> ArgumentError
 *   C.new.method(:d).to_proc.lambda?   #=> true
 *
 * +define_method+ always defines a method without the tricks,
 * even if a non-lambda Proc object is given.
 * This is the only exception for which the tricks are not preserved.
 *
 *   class C
 *     define_method(:e, &proc {})
 *   end
 *   C.new.e(1,2)       #=> ArgumentError
 *   C.new.method(:e).to_proc.lambda?   #=> true
 *
 * This exception insures that methods never have tricks
 * and makes it easy to have wrappers to define methods that behave as usual.
 *
 *   class C
 *     def self.def2(name, &body)
 *       define_method(name, &body)
 *     end
 *
 *     def2(:f) {}
 *   end
 *   C.new.f(1,2)       #=> ArgumentError
 *
 * The wrapper <i>def2</i> defines a method which has no tricks.
 *
 */

VALUE
rb_proc_lambda_p(VALUE procval)
{
    rb_proc_t *proc;
    GetProcPtr(procval, proc);

    return proc->is_lambda ? Qtrue : Qfalse;
}

/* Binding */

static void
binding_free(void *ptr)
{
    rb_binding_t *bind;
    RUBY_FREE_ENTER("binding");
    if (ptr) {
	bind = ptr;
	ruby_xfree(bind);
    }
    RUBY_FREE_LEAVE("binding");
}

static void
binding_mark(void *ptr)
{
    rb_binding_t *bind = ptr;

    RUBY_MARK_ENTER("binding");

    RUBY_MARK_UNLESS_NULL(bind->env);
    RUBY_MARK_UNLESS_NULL(bind->path);

    RUBY_MARK_LEAVE("binding");
}

static size_t
binding_memsize(const void *ptr)
{
    return sizeof(rb_binding_t);
}

const rb_data_type_t ruby_binding_data_type = {
    "binding",
    {
	binding_mark,
	binding_free,
	binding_memsize,
    },
    0, 0, RUBY_TYPED_FREE_IMMEDIATELY
};

VALUE
rb_binding_alloc(VALUE klass)
{
    VALUE obj;
    rb_binding_t *bind;
    obj = TypedData_Make_Struct(klass, rb_binding_t, &ruby_binding_data_type, bind);
    return obj;
}

/* :nodoc: */
static VALUE
binding_dup(VALUE self)
{
    VALUE bindval = rb_binding_alloc(rb_cBinding);
    rb_binding_t *src, *dst;
    GetBindingPtr(self, src);
    GetBindingPtr(bindval, dst);
    dst->env = src->env;
    dst->path = src->path;
    dst->first_lineno = src->first_lineno;
    return bindval;
}

/* :nodoc: */
static VALUE
binding_clone(VALUE self)
{
    VALUE bindval = binding_dup(self);
    CLONESETUP(bindval, self);
    return bindval;
}

VALUE
rb_binding_new(void)
{
    rb_thread_t *th = GET_THREAD();
    return rb_vm_make_binding(th, th->cfp);
}

/*
 *  call-seq:
 *     binding -> a_binding
 *
 *  Returns a +Binding+ object, describing the variable and
 *  method bindings at the point of call. This object can be used when
 *  calling +eval+ to execute the evaluated command in this
 *  environment. See also the description of class +Binding+.
 *
 *     def get_binding(param)
 *       return binding
 *     end
 *     b = get_binding("hello")
 *     eval("param", b)   #=> "hello"
 */

static VALUE
rb_f_binding(VALUE self)
{
    return rb_binding_new();
}

/*
 *  call-seq:
 *     binding.eval(string [, filename [,lineno]])  -> obj
 *
 *  Evaluates the Ruby expression(s) in <em>string</em>, in the
 *  <em>binding</em>'s context.  If the optional <em>filename</em> and
 *  <em>lineno</em> parameters are present, they will be used when
 *  reporting syntax errors.
 *
 *     def get_binding(param)
 *       return binding
 *     end
 *     b = get_binding("hello")
 *     b.eval("param")   #=> "hello"
 */

static VALUE
bind_eval(int argc, VALUE *argv, VALUE bindval)
{
    VALUE args[4];

    rb_scan_args(argc, argv, "12", &args[0], &args[2], &args[3]);
    args[1] = bindval;
    return rb_f_eval(argc+1, args, Qnil /* self will be searched in eval */);
}

static VALUE *
get_local_variable_ptr(VALUE envval, ID lid)
{
    rb_env_t *env;

    do {
	const rb_iseq_t *iseq;
	unsigned int i;

	GetEnvPtr(envval, env);
	iseq = env->block.iseq;

	if (RUBY_VM_NORMAL_ISEQ_P(iseq)) {
	    for (i=0; i<iseq->body->local_table_size; i++) {
		if (iseq->body->local_table[i] == lid) {
		    return &env->env[i];
		}
	    }
	}
	else {
	    return NULL;
	}
    } while ((envval = rb_vm_env_prev_envval(env)) != Qfalse);

    return NULL;
}

/*
 * check local variable name.
 * returns ID if it's an already interned symbol, or 0 with setting
 * local name in String to *namep.
 */
static ID
check_local_id(VALUE bindval, volatile VALUE *pname)
{
    ID lid = rb_check_id(pname);
    VALUE name = *pname;

    if (lid) {
	if (!rb_is_local_id(lid)) {
	    rb_name_err_raise("wrong local variable name `%1$s' for %2$s",
			      bindval, ID2SYM(lid));
	}
    }
    else {
	if (!rb_is_local_name(name)) {
	    rb_name_err_raise("wrong local variable name `%1$s' for %2$s",
			      bindval, name);
	}
	return 0;
    }
    return lid;
}

/*
 *  call-seq:
 *     binding.local_variables -> Array
 *
 *  Returns the +symbol+ names of the binding's local variables
 *
 *	def foo
 *  	  a = 1
 *  	  2.times do |n|
 *  	    binding.local_variables #=> [:a, :n]
 *  	  end
 *  	end
 *
 *  This method is short version of the following code.
 *
 *	binding.eval("local_variables")
 *
 */
static VALUE
bind_local_variables(VALUE bindval)
{
    const rb_binding_t *bind;
    const rb_env_t *env;

    GetBindingPtr(bindval, bind);
    GetEnvPtr(bind->env, env);

    return rb_vm_env_local_variables(env);
}

/*
 *  call-seq:
 *     binding.local_variable_get(symbol) -> obj
 *
 *  Returns a +value+ of local variable +symbol+.
 *
 *	def foo
 *  	  a = 1
 *  	  binding.local_variable_get(:a) #=> 1
 *  	  binding.local_variable_get(:b) #=> NameError
 *  	end
 *
 *  This method is short version of the following code.
 *
 *	binding.eval("#{symbol}")
 *
 */
static VALUE
bind_local_variable_get(VALUE bindval, VALUE sym)
{
    ID lid = check_local_id(bindval, &sym);
    const rb_binding_t *bind;
    const VALUE *ptr;

    if (!lid) goto undefined;

    GetBindingPtr(bindval, bind);

    if ((ptr = get_local_variable_ptr(bind->env, lid)) == NULL) {
	sym = ID2SYM(lid);
      undefined:
	rb_name_err_raise("local variable `%1$s' not defined for %2$s",
			  bindval, sym);
    }

    return *ptr;
}

/*
 *  call-seq:
 *     binding.local_variable_set(symbol, obj) -> obj
 *
 *  Set local variable named +symbol+ as +obj+.
 *
 *	def foo
 *  	  a = 1
 *  	  bind = binding
 *  	  bind.local_variable_set(:a, 2) # set existing local variable `a'
 *  	  bind.local_variable_set(:b, 3) # create new local variable `b'
 *  	                                 # `b' exists only in binding.
 *  	  p bind.local_variable_get(:a) #=> 2
 *  	  p bind.local_variable_get(:b) #=> 3
 *  	  p a #=> 2
 *  	  p b #=> NameError
 *  	end
 *
 *  This method is a similar behavior of the following code
 *
 *    binding.eval("#{symbol} = #{obj}")
 *
 *  if obj can be dumped in Ruby code.
 */
static VALUE
bind_local_variable_set(VALUE bindval, VALUE sym, VALUE val)
{
    ID lid = check_local_id(bindval, &sym);
    rb_binding_t *bind;
    VALUE *ptr;

    if (!lid) lid = rb_intern_str(sym);

    GetBindingPtr(bindval, bind);
    if ((ptr = get_local_variable_ptr(bind->env, lid)) == NULL) {
	/* not found. create new env */
	ptr = rb_binding_add_dynavars(bind, 1, &lid);
    }

    *ptr = val;

    return val;
}

/*
 *  call-seq:
 *     binding.local_variable_defined?(symbol) -> obj
 *
 *  Returns a +true+ if a local variable +symbol+ exists.
 *
 *	def foo
 *  	  a = 1
 *  	  binding.local_variable_defined?(:a) #=> true
 *  	  binding.local_variable_defined?(:b) #=> false
 *  	end
 *
 *  This method is short version of the following code.
 *
 *	binding.eval("defined?(#{symbol}) == 'local-variable'")
 *
 */
static VALUE
bind_local_variable_defined_p(VALUE bindval, VALUE sym)
{
    ID lid = check_local_id(bindval, &sym);
    const rb_binding_t *bind;

    if (!lid) return Qfalse;

    GetBindingPtr(bindval, bind);
    return get_local_variable_ptr(bind->env, lid) ? Qtrue : Qfalse;
}

/*
 *  call-seq:
 *     binding.receiver    -> object
 *
 *  Returns the bound receiver of the binding object.
 */
static VALUE
bind_receiver(VALUE bindval)
{
    const rb_binding_t *bind;
    const rb_env_t *env;

    GetBindingPtr(bindval, bind);
    GetEnvPtr(bind->env, env);
    return env->block.self;
}

static VALUE
cfunc_proc_new(VALUE klass, VALUE ifunc, int8_t is_lambda)
{
    rb_proc_t *proc;
    cfunc_proc_t *sproc;
    VALUE procval = TypedData_Make_Struct(klass, cfunc_proc_t, &proc_data_type, sproc);
    sproc->env[1] = VM_ENVVAL_BLOCK_PTR(0);
    proc = &sproc->basic;
    proc->block.ep = sproc->env+1;
    proc->block.iseq = (rb_iseq_t *)ifunc;
    proc->block.proc = procval;
    proc->is_lambda = is_lambda;
    return procval;
}

static VALUE
sym_proc_new(VALUE klass, VALUE sym)
{
    return cfunc_proc_new(klass, sym, 0);
}

VALUE
rb_func_proc_new(rb_block_call_func_t func, VALUE val)
{
    return cfunc_proc_new(rb_cProc, (VALUE)IFUNC_NEW(func, val, 0), 0);
}

VALUE
rb_func_lambda_new(rb_block_call_func_t func, VALUE val)
{
    return cfunc_proc_new(rb_cProc, (VALUE)IFUNC_NEW(func, val, 0), 1);
}

static const char proc_without_block[] = "tried to create Proc object without a block";

static VALUE
proc_new(VALUE klass, int8_t is_lambda)
{
    VALUE procval = Qnil;
    rb_thread_t *th = GET_THREAD();
    rb_control_frame_t *cfp = th->cfp;
    rb_block_t *block;

    if (!(block = rb_vm_control_frame_block_ptr(cfp))) {
#if !PROC_NEW_REQUIRES_BLOCK
	cfp = RUBY_VM_PREVIOUS_CONTROL_FRAME(cfp);

	if ((block = rb_vm_control_frame_block_ptr(cfp)) != 0) {
	    if (is_lambda) {
		rb_warn(proc_without_block);
	    }
	}
#else
	if (0)
#endif
	else {
	    rb_raise(rb_eArgError, proc_without_block);
	}
    }

    procval = block->proc;

    if (procval) {
	if (SYMBOL_P(procval)) {
	    return (klass != rb_cProc) ? sym_proc_new(klass, procval) : rb_sym_to_proc(procval);
	}
	else if (RBASIC_CLASS(procval) == klass) {
	    return procval;
	}
	else {
	    VALUE newprocval = proc_dup(procval);
	    RBASIC_SET_CLASS(newprocval, klass);
	    return newprocval;
	}
    }

    procval = rb_vm_make_proc_lambda(th, block, klass, is_lambda);
    return procval;
}

/*
 *  call-seq:
 *     Proc.new {|...| block } -> a_proc
 *     Proc.new                -> a_proc
 *
 *  Creates a new <code>Proc</code> object, bound to the current
 *  context. <code>Proc::new</code> may be called without a block only
 *  within a method with an attached block, in which case that block is
 *  converted to the <code>Proc</code> object.
 *
 *     def proc_from
 *       Proc.new
 *     end
 *     proc = proc_from { "hello" }
 *     proc.call   #=> "hello"
 */

static VALUE
rb_proc_s_new(int argc, VALUE *argv, VALUE klass)
{
    VALUE block = proc_new(klass, FALSE);

    rb_obj_call_init(block, argc, argv);
    return block;
}

/*
 * call-seq:
 *   proc   { |...| block }  -> a_proc
 *
 * Equivalent to <code>Proc.new</code>.
 */

VALUE
rb_block_proc(void)
{
    return proc_new(rb_cProc, FALSE);
}

/*
 * call-seq:
 *   lambda { |...| block }  -> a_proc
 *
 * Equivalent to <code>Proc.new</code>, except the resulting Proc objects
 * check the number of parameters passed when called.
 */

VALUE
rb_block_lambda(void)
{
    return proc_new(rb_cProc, TRUE);
}

/*  Document-method: ===
 *
 *  call-seq:
 *     proc === obj   -> result_of_proc
 *
 *  Invokes the block with +obj+ as the proc's parameter like Proc#call.  It
 *  is to allow a proc object to be a target of +when+ clause in a case
 *  statement.
 */

/* CHECKME: are the argument checking semantics correct? */

/*
 *  call-seq:
 *     prc.call(params,...)   -> obj
 *     prc[params,...]        -> obj
 *     prc.(params,...)       -> obj
 *
 *  Invokes the block, setting the block's parameters to the values in
 *  <i>params</i> using something close to method calling semantics.
 *  Generates a warning if multiple values are passed to a proc that
 *  expects just one (previously this silently converted the parameters
 *  to an array).  Note that <code>prc.()</code> invokes
 *  <code>prc.call()</code> with the parameters given.  It's a syntax sugar to
 *  hide "call".
 *
 *  Returns the value of the last expression evaluated in the block. See
 *  also Proc#yield.
 *
 *     a_proc = Proc.new { |scalar, *values| values.collect { |value| value*scalar } }
 *     a_proc.call(9, 1, 2, 3)   #=> [9, 18, 27]
 *     a_proc[9, 1, 2, 3]        #=> [9, 18, 27]
 *     a_proc.(9, 1, 2, 3)       #=> [9, 18, 27]
 *
 *  For procs created using <code>lambda</code> or <code>->()</code> an error
 *  is generated if the wrong number of parameters are passed to a Proc with
 *  multiple parameters.  For procs created using <code>Proc.new</code> or
 *  <code>Kernel.proc</code>, extra parameters are silently discarded.
 *
 *     a_proc = lambda {|a,b| a}
 *     a_proc.call(1,2,3)
 *
 *  <em>produces:</em>
 *
 *     prog.rb:4:in `block in <main>': wrong number of arguments (given 3, expected 2) (ArgumentError)
 *     	from prog.rb:5:in `call'
 *     	from prog.rb:5:in `<main>'
 *
 */
#if 0
static VALUE
proc_call(int argc, VALUE *argv, VALUE procval)
{
    VALUE vret;
    const rb_block_t *blockptr = 0;
    const rb_iseq_t *iseq;
    rb_proc_t *proc;
    VALUE passed_procval;
    GetProcPtr(procval, proc);

    iseq = proc->block.iseq;
    if (RUBY_VM_IFUNC_P(iseq) || iseq->body->param.flags.has_block) {
	if (rb_block_given_p()) {
	    rb_proc_t *passed_proc;
	    passed_procval = rb_block_proc();
	    GetProcPtr(passed_procval, passed_proc);
	    blockptr = &passed_proc->block;
	}
    }

    vret = rb_vm_invoke_proc(GET_THREAD(), proc, argc, argv, blockptr);
    RB_GC_GUARD(procval);
    RB_GC_GUARD(passed_procval);
    return vret;
}
#endif

#if SIZEOF_LONG > SIZEOF_INT
static inline int
check_argc(long argc)
{
    if (argc > INT_MAX || argc < 0) {
	rb_raise(rb_eArgError, "too many arguments (%lu)",
		 (unsigned long)argc);
    }
    return (int)argc;
}
#else
#define check_argc(argc) (argc)
#endif

VALUE
rb_proc_call(VALUE self, VALUE args)
{
    VALUE vret;
    rb_proc_t *proc;
    GetProcPtr(self, proc);
    vret = rb_vm_invoke_proc(GET_THREAD(), proc, check_argc(RARRAY_LEN(args)), RARRAY_CONST_PTR(args), 0);
    RB_GC_GUARD(self);
    RB_GC_GUARD(args);
    return vret;
}

VALUE
rb_proc_call_with_block(VALUE self, int argc, const VALUE *argv, VALUE pass_procval)
{
    VALUE vret;
    rb_proc_t *proc;
    rb_block_t *block = 0;
    GetProcPtr(self, proc);

    if (!NIL_P(pass_procval)) {
	rb_proc_t *pass_proc;
	GetProcPtr(pass_procval, pass_proc);
	block = &pass_proc->block;
    }

    vret = rb_vm_invoke_proc(GET_THREAD(), proc, argc, argv, block);
    RB_GC_GUARD(self);
    RB_GC_GUARD(pass_procval);
    return vret;
}


/*
 *  call-seq:
 *     prc.arity -> fixnum
 *
 *  Returns the number of mandatory arguments. If the block
 *  is declared to take no arguments, returns 0. If the block is known
 *  to take exactly n arguments, returns n.
 *  If the block has optional arguments, returns -n-1, where n is the
 *  number of mandatory arguments, with the exception for blocks that
 *  are not lambdas and have only a finite number of optional arguments;
 *  in this latter case, returns n.
 *  Keywords arguments will considered as a single additional argument,
 *  that argument being mandatory if any keyword argument is mandatory.
 *  A <code>proc</code> with no argument declarations
 *  is the same as a block declaring <code>||</code> as its arguments.
 *
 *     proc {}.arity                  #=>  0
 *     proc { || }.arity              #=>  0
 *     proc { |a| }.arity             #=>  1
 *     proc { |a, b| }.arity          #=>  2
 *     proc { |a, b, c| }.arity       #=>  3
 *     proc { |*a| }.arity            #=> -1
 *     proc { |a, *b| }.arity         #=> -2
 *     proc { |a, *b, c| }.arity      #=> -3
 *     proc { |x:, y:, z:0| }.arity   #=>  1
 *     proc { |*a, x:, y:0| }.arity   #=> -2
 *
 *     proc   { |x=0| }.arity         #=>  0
 *     lambda { |x=0| }.arity         #=> -1
 *     proc   { |x=0, y| }.arity      #=>  1
 *     lambda { |x=0, y| }.arity      #=> -2
 *     proc   { |x=0, y=0| }.arity    #=>  0
 *     lambda { |x=0, y=0| }.arity    #=> -1
 *     proc   { |x, y=0| }.arity      #=>  1
 *     lambda { |x, y=0| }.arity      #=> -2
 *     proc   { |(x, y), z=0| }.arity #=>  1
 *     lambda { |(x, y), z=0| }.arity #=> -2
 *     proc   { |a, x:0, y:0| }.arity #=>  1
 *     lambda { |a, x:0, y:0| }.arity #=> -2
 */

static VALUE
proc_arity(VALUE self)
{
    int arity = rb_proc_arity(self);
    return INT2FIX(arity);
}

static inline int
rb_iseq_min_max_arity(const rb_iseq_t *iseq, int *max)
{
    *max = iseq->body->param.flags.has_rest == FALSE ?
      iseq->body->param.lead_num + iseq->body->param.opt_num + iseq->body->param.post_num +
      (iseq->body->param.flags.has_kw == TRUE || iseq->body->param.flags.has_kwrest == TRUE)
      : UNLIMITED_ARGUMENTS;
    return iseq->body->param.lead_num + iseq->body->param.post_num + (iseq->body->param.flags.has_kw && iseq->body->param.keyword->required_num > 0);
}

static int
rb_block_min_max_arity(rb_block_t *block, int *max)
{
    const rb_iseq_t *iseq = block->iseq;

    if (iseq) {
	if (RUBY_VM_NORMAL_ISEQ_P(iseq)) {
	    return rb_iseq_min_max_arity(iseq, max);
	}
	else {
	    if (IS_METHOD_PROC_ISEQ(iseq)) {
		const struct vm_ifunc *ifunc = (struct vm_ifunc *)iseq;
		/* e.g. method(:foo).to_proc.arity */
		return method_min_max_arity((VALUE)ifunc->data, max);
	    }
	}
    }
    *max = UNLIMITED_ARGUMENTS;
    return 0;
}

/*
 * Returns the number of required parameters and stores the maximum
 * number of parameters in max, or UNLIMITED_ARGUMENTS if no max.
 * For non-lambda procs, the maximum is the number of non-ignored
 * parameters even though there is no actual limit to the number of parameters
 */
static int
rb_proc_min_max_arity(VALUE self, int *max)
{
    rb_proc_t *proc;
    rb_block_t *block;
    GetProcPtr(self, proc);
    block = &proc->block;
    return rb_block_min_max_arity(block, max);
}

int
rb_proc_arity(VALUE self)
{
    rb_proc_t *proc;
    int max, min = rb_proc_min_max_arity(self, &max);
    GetProcPtr(self, proc);
    return (proc->is_lambda ? min == max : max != UNLIMITED_ARGUMENTS) ? min : -min-1;
}

int
rb_block_arity(void)
{
    int min, max;
    rb_thread_t *th = GET_THREAD();
    rb_control_frame_t *cfp = th->cfp;
    rb_block_t *block = rb_vm_control_frame_block_ptr(cfp);
    VALUE proc_value;

    if (!block) rb_raise(rb_eArgError, "no block given");
    min = rb_block_min_max_arity(block, &max);
    proc_value = block->proc;
    if (proc_value) {
	if (SYMBOL_P(proc_value)) {
	    return -1;
	}
	else {
	    rb_proc_t *proc;
	    GetProcPtr(proc_value, proc);
	    if (proc)
		return (proc->is_lambda ? min == max : max != UNLIMITED_ARGUMENTS) ? min : -min-1;
	}
    }
    return max != UNLIMITED_ARGUMENTS ? min : -min-1;
}

const rb_iseq_t *
rb_proc_get_iseq(VALUE self, int *is_proc)
{
    const rb_proc_t *proc;
    const rb_iseq_t *iseq;

    GetProcPtr(self, proc);
    iseq = proc->block.iseq;
    if (is_proc) *is_proc = !proc->is_lambda;
    if (RUBY_VM_IFUNC_P(iseq)) {
	const struct vm_ifunc *ifunc = (struct vm_ifunc *)iseq;
	iseq = 0;
	if (IS_METHOD_PROC_IFUNC(ifunc)) {
	    /* method(:foo).to_proc */
	    iseq = rb_method_iseq((VALUE)ifunc->data);
	    if (is_proc) *is_proc = 0;
	}
	return iseq;
    }
    else if (SYMBOL_P(iseq)) {
	return NULL;
    }
    else {
	return rb_iseq_check(iseq);
    }
}

static VALUE
iseq_location(const rb_iseq_t *iseq)
{
    VALUE loc[2];

    if (!iseq) return Qnil;
    rb_iseq_check(iseq);
    loc[0] = iseq->body->location.path;
    if (iseq->body->line_info_table) {
	loc[1] = rb_iseq_first_lineno(iseq);
    }
    else {
	loc[1] = Qnil;
    }
    return rb_ary_new4(2, loc);
}

/*
 * call-seq:
 *    prc.source_location  -> [String, Fixnum]
 *
 * Returns the Ruby source filename and line number containing this proc
 * or +nil+ if this proc was not defined in Ruby (i.e. native)
 */

VALUE
rb_proc_location(VALUE self)
{
    return iseq_location(rb_proc_get_iseq(self, 0));
}

static VALUE
unnamed_parameters(int arity)
{
    VALUE a, param = rb_ary_new2((arity < 0) ? -arity : arity);
    int n = (arity < 0) ? ~arity : arity;
    ID req, rest;
    CONST_ID(req, "req");
    a = rb_ary_new3(1, ID2SYM(req));
    OBJ_FREEZE(a);
    for (; n; --n) {
	rb_ary_push(param, a);
    }
    if (arity < 0) {
	CONST_ID(rest, "rest");
	rb_ary_store(param, ~arity, rb_ary_new3(1, ID2SYM(rest)));
    }
    return param;
}

/*
 * call-seq:
 *    prc.parameters  -> array
 *
 * Returns the parameter information of this proc.
 *
 *    prc = lambda{|x, y=42, *other|}
 *    prc.parameters  #=> [[:req, :x], [:opt, :y], [:rest, :other]]
 */

static VALUE
rb_proc_parameters(VALUE self)
{
    int is_proc;
    const rb_iseq_t *iseq = rb_proc_get_iseq(self, &is_proc);
    if (!iseq) {
	return unnamed_parameters(rb_proc_arity(self));
    }
    return rb_iseq_parameters(iseq, is_proc);
}

st_index_t
rb_hash_proc(st_index_t hash, VALUE prc)
{
    rb_proc_t *proc;
    GetProcPtr(prc, proc);
    hash = rb_hash_uint(hash, (st_index_t)proc->block.iseq);
    return rb_hash_uint(hash, (st_index_t)proc->block.ep >> 16);
}

VALUE
rb_sym_to_proc(VALUE sym)
{
    static VALUE sym_proc_cache = Qfalse;
    enum {SYM_PROC_CACHE_SIZE = 67};
    VALUE proc;
    long index;
    ID id;
    VALUE *aryp;

    if (!sym_proc_cache) {
	sym_proc_cache = rb_ary_tmp_new(SYM_PROC_CACHE_SIZE * 2);
	rb_gc_register_mark_object(sym_proc_cache);
	rb_ary_store(sym_proc_cache, SYM_PROC_CACHE_SIZE*2 - 1, Qnil);
    }

    id = SYM2ID(sym);
    index = (id % SYM_PROC_CACHE_SIZE) << 1;

    aryp = RARRAY_PTR(sym_proc_cache);
    if (aryp[index] == sym) {
	return aryp[index + 1];
    }
    else {
	proc = sym_proc_new(rb_cProc, ID2SYM(id));
	aryp[index] = sym;
	aryp[index + 1] = proc;
	return proc;
    }
}

/*
 * call-seq:
 *   prc.hash   ->  integer
 *
 * Returns a hash value corresponding to proc body.
 *
 * See also Object#hash.
 */

static VALUE
proc_hash(VALUE self)
{
    st_index_t hash;
    hash = rb_hash_start(0);
    hash = rb_hash_proc(hash, self);
    hash = rb_hash_end(hash);
    return LONG2FIX(hash);
}

/*
 * call-seq:
 *   prc.to_s   -> string
 *
 * Returns the unique identifier for this proc, along with
 * an indication of where the proc was defined.
 */

static VALUE
proc_to_s(VALUE self)
{
    VALUE str = 0;
    rb_proc_t *proc;
    const char *cname = rb_obj_classname(self);
    const rb_iseq_t *iseq;
    const char *is_lambda;

    GetProcPtr(self, proc);
    iseq = proc->block.iseq;
    is_lambda = proc->is_lambda ? " (lambda)" : "";

    if (RUBY_VM_NORMAL_ISEQ_P(iseq) && rb_iseq_check(iseq)) {
	int first_lineno = 0;

	if (iseq->body->line_info_table) {
	    first_lineno = FIX2INT(rb_iseq_first_lineno(iseq));
	}
	str = rb_sprintf("#<%s:%p@%"PRIsVALUE":%d%s>", cname, (void *)self,
			 iseq->body->location.path, first_lineno, is_lambda);
    }
    else if (SYMBOL_P(iseq)) {
	str = rb_sprintf("#<%s:%p(&%+"PRIsVALUE")%s>", cname, (void *)self,
			 (VALUE)iseq, is_lambda);
    }
    else {
	str = rb_sprintf("#<%s:%p%s>", cname, (void *)proc->block.iseq,
			 is_lambda);
    }

    if (OBJ_TAINTED(self)) {
	OBJ_TAINT(str);
    }
    return str;
}

/*
 *  call-seq:
 *     prc.to_proc -> proc
 *
 *  Part of the protocol for converting objects to <code>Proc</code>
 *  objects. Instances of class <code>Proc</code> simply return
 *  themselves.
 */

static VALUE
proc_to_proc(VALUE self)
{
    return self;
}

static void
bm_mark(void *ptr)
{
    struct METHOD *data = ptr;
    rb_gc_mark(data->recv);
    rb_gc_mark(data->klass);
    rb_gc_mark((VALUE)data->me);
}

static size_t
bm_memsize(const void *ptr)
{
    return sizeof(struct METHOD);
}

static const rb_data_type_t method_data_type = {
    "method",
    {
	bm_mark,
	RUBY_TYPED_DEFAULT_FREE,
	bm_memsize,
    },
    0, 0, RUBY_TYPED_FREE_IMMEDIATELY
};

VALUE
rb_obj_is_method(VALUE m)
{
    if (rb_typeddata_is_kind_of(m, &method_data_type)) {
	return Qtrue;
    }
    else {
	return Qfalse;
    }
}

static int
respond_to_missing_p(VALUE klass, VALUE obj, VALUE sym, int scope)
{
    /* TODO: merge with obj_respond_to() */
    ID rmiss = idRespond_to_missing;

    if (obj == Qundef) return 0;
    if (rb_method_basic_definition_p(klass, rmiss)) return 0;
    return RTEST(rb_funcall(obj, rmiss, 2, sym, scope ? Qfalse : Qtrue));
}


static VALUE
mnew_missing(VALUE klass, VALUE obj, ID id, ID rid, VALUE mclass)
{
    struct METHOD *data;
    VALUE method = TypedData_Make_Struct(mclass, struct METHOD, &method_data_type, data);
    rb_method_entry_t *me;
    rb_method_definition_t *def;

    RB_OBJ_WRITE(method, &data->recv, obj);
    RB_OBJ_WRITE(method, &data->klass, klass);

    def = ZALLOC(rb_method_definition_t);
    def->type = VM_METHOD_TYPE_MISSING;
    def->original_id = id;

    me = rb_method_entry_create(id, klass, METHOD_VISI_UNDEF, def);

    RB_OBJ_WRITE(method, &data->me, me);

    OBJ_INFECT(method, klass);

    return method;
}

static VALUE
mnew_internal(const rb_method_entry_t *me, VALUE klass,
	      VALUE obj, ID id, VALUE mclass, int scope, int error)
{
    struct METHOD *data;
    VALUE method;
    ID rid = id;
    rb_method_visibility_t visi = METHOD_VISI_UNDEF;

  again:
    if (UNDEFINED_METHOD_ENTRY_P(me)) {
	if (respond_to_missing_p(klass, obj, ID2SYM(id), scope)) {
	    return mnew_missing(klass, obj, id, rid, mclass);
	}
	if (!error) return Qnil;
	rb_print_undef(klass, id, METHOD_VISI_UNDEF);
    }
    if (visi == METHOD_VISI_UNDEF) {
	visi = METHOD_ENTRY_VISI(me);
	if (scope && (visi != METHOD_VISI_PUBLIC)) {
	    if (!error) return Qnil;
	    rb_print_inaccessible(klass, id, visi);
	}
    }
    if (me->def->type == VM_METHOD_TYPE_ZSUPER) {
	if (me->defined_class) {
	    VALUE klass = RCLASS_SUPER(me->defined_class);
	    id = me->def->original_id;
	    me = (rb_method_entry_t *)rb_callable_method_entry_without_refinements(klass, id);
	}
	else {
	    VALUE klass = RCLASS_SUPER(me->owner);
	    id = me->def->original_id;
	    me = rb_method_entry_without_refinements(klass, id);
	}
	goto again;
    }

    while (klass != me->owner && (FL_TEST(klass, FL_SINGLETON) || RB_TYPE_P(klass, T_ICLASS))) {
	klass = RCLASS_SUPER(klass);
    }

    method = TypedData_Make_Struct(mclass, struct METHOD, &method_data_type, data);

    RB_OBJ_WRITE(method, &data->recv, obj);
    RB_OBJ_WRITE(method, &data->klass, klass);
    RB_OBJ_WRITE(method, &data->me, me);

    OBJ_INFECT(method, klass);
    return method;
}

static VALUE
mnew_from_me(const rb_method_entry_t *me, VALUE klass,
	     VALUE obj, ID id, VALUE mclass, int scope)
{
    return mnew_internal(me, klass, obj, id, mclass, scope, TRUE);
}

static VALUE
mnew(VALUE klass, VALUE obj, ID id, VALUE mclass, int scope)
{
    const rb_method_entry_t *me;

    if (obj == Qundef) { /* UnboundMethod */
	me = rb_method_entry_without_refinements(klass, id);
    }
    else {
	me = (rb_method_entry_t *)rb_callable_method_entry_without_refinements(klass, id);
    }
    return mnew_from_me(me, klass, obj, id, mclass, scope);
}

static inline VALUE
method_entry_defined_class(const rb_method_entry_t *me)
{
    VALUE defined_class = me->defined_class;
    return defined_class ? defined_class : me->owner;
}

/**********************************************************************
 *
 * Document-class : Method
 *
 *  Method objects are created by <code>Object#method</code>, and are
 *  associated with a particular object (not just with a class). They
 *  may be used to invoke the method within the object, and as a block
 *  associated with an iterator. They may also be unbound from one
 *  object (creating an <code>UnboundMethod</code>) and bound to
 *  another.
 *
 *     class Thing
 *       def square(n)
 *         n*n
 *       end
 *     end
 *     thing = Thing.new
 *     meth  = thing.method(:square)
 *
 *     meth.call(9)                 #=> 81
 *     [ 1, 2, 3 ].collect(&meth)   #=> [1, 4, 9]
 *
 */

/*
 * call-seq:
 *   meth.eql?(other_meth)  -> true or false
 *   meth == other_meth  -> true or false
 *
 * Two method objects are equal if they are bound to the same
 * object and refer to the same method definition and their owners are the
 * same class or module.
 */

static VALUE
method_eq(VALUE method, VALUE other)
{
    struct METHOD *m1, *m2;
    VALUE klass1, klass2;

    if (!rb_obj_is_method(other))
	return Qfalse;
    if (CLASS_OF(method) != CLASS_OF(other))
	return Qfalse;

    Check_TypedStruct(method, &method_data_type);
    m1 = (struct METHOD *)DATA_PTR(method);
    m2 = (struct METHOD *)DATA_PTR(other);

    klass1 = method_entry_defined_class(m1->me);
    klass2 = method_entry_defined_class(m2->me);

    if (!rb_method_entry_eq(m1->me, m2->me) ||
	klass1 != klass2 ||
	m1->klass != m2->klass ||
	m1->recv != m2->recv) {
	return Qfalse;
    }

    return Qtrue;
}

/*
 * call-seq:
 *    meth.hash   -> integer
 *
 * Returns a hash value corresponding to the method object.
 *
 * See also Object#hash.
 */

static VALUE
method_hash(VALUE method)
{
    struct METHOD *m;
    st_index_t hash;

    TypedData_Get_Struct(method, struct METHOD, &method_data_type, m);
    hash = rb_hash_start((st_index_t)m->recv);
    hash = rb_hash_method_entry(hash, m->me);
    hash = rb_hash_end(hash);

    return INT2FIX(hash);
}

/*
 *  call-seq:
 *     meth.unbind    -> unbound_method
 *
 *  Dissociates <i>meth</i> from its current receiver. The resulting
 *  <code>UnboundMethod</code> can subsequently be bound to a new object
 *  of the same class (see <code>UnboundMethod</code>).
 */

static VALUE
method_unbind(VALUE obj)
{
    VALUE method;
    struct METHOD *orig, *data;

    TypedData_Get_Struct(obj, struct METHOD, &method_data_type, orig);
    method = TypedData_Make_Struct(rb_cUnboundMethod, struct METHOD,
				   &method_data_type, data);
    RB_OBJ_WRITE(method, &data->recv, Qundef);
    RB_OBJ_WRITE(method, &data->klass, orig->klass);
    RB_OBJ_WRITE(method, &data->me, rb_method_entry_clone(orig->me));
    OBJ_INFECT(method, obj);

    return method;
}

/*
 *  call-seq:
 *     meth.receiver    -> object
 *
 *  Returns the bound receiver of the method object.
 */

static VALUE
method_receiver(VALUE obj)
{
    struct METHOD *data;

    TypedData_Get_Struct(obj, struct METHOD, &method_data_type, data);
    return data->recv;
}

/*
 *  call-seq:
 *     meth.name    -> symbol
 *
 *  Returns the name of the method.
 */

static VALUE
method_name(VALUE obj)
{
    struct METHOD *data;

    TypedData_Get_Struct(obj, struct METHOD, &method_data_type, data);
    return ID2SYM(data->me->called_id);
}

/*
 *  call-seq:
 *     meth.original_name    -> symbol
 *
 *  Returns the original name of the method.
 */

static VALUE
method_original_name(VALUE obj)
{
    struct METHOD *data;

    TypedData_Get_Struct(obj, struct METHOD, &method_data_type, data);
    return ID2SYM(data->me->def->original_id);
}

/*
 *  call-seq:
 *     meth.owner    -> class_or_module
 *
 *  Returns the class or module that defines the method.
 */

static VALUE
method_owner(VALUE obj)
{
    struct METHOD *data;
    TypedData_Get_Struct(obj, struct METHOD, &method_data_type, data);
    return data->me->owner;
}

void
rb_method_name_error(VALUE klass, VALUE str)
{
#define MSG(s) rb_fstring_cstr("undefined method `%1$s' for"s" `%2$s'")
    VALUE c = klass;
    VALUE s;

    if (FL_TEST(c, FL_SINGLETON)) {
	VALUE obj = rb_ivar_get(klass, attached);

	switch (BUILTIN_TYPE(obj)) {
	  case T_MODULE:
	  case T_CLASS:
	    c = obj;
	    s = MSG("");
	}
	goto normal_class;
    }
    else if (RB_TYPE_P(c, T_MODULE)) {
	s = MSG(" module");
    }
    else {
      normal_class:
	s = MSG(" class");
    }
    rb_name_err_raise_str(s, c, str);
#undef MSG
}

static VALUE
obj_method(VALUE obj, VALUE vid, int scope)
{
    ID id = rb_check_id(&vid);
    const VALUE klass = CLASS_OF(obj);
    const VALUE mclass = rb_cMethod;

    if (!id) {
	if (respond_to_missing_p(klass, obj, vid, scope)) {
	    id = rb_intern_str(vid);
	    return mnew_missing(klass, obj, id, id, mclass);
	}
	rb_method_name_error(klass, vid);
    }
    return mnew(klass, obj, id, mclass, scope);
}

/*
 *  call-seq:
 *     obj.method(sym)    -> method
 *
 *  Looks up the named method as a receiver in <i>obj</i>, returning a
 *  <code>Method</code> object (or raising <code>NameError</code>). The
 *  <code>Method</code> object acts as a closure in <i>obj</i>'s object
 *  instance, so instance variables and the value of <code>self</code>
 *  remain available.
 *
 *     class Demo
 *       def initialize(n)
 *         @iv = n
 *       end
 *       def hello()
 *         "Hello, @iv = #{@iv}"
 *       end
 *     end
 *
 *     k = Demo.new(99)
 *     m = k.method(:hello)
 *     m.call   #=> "Hello, @iv = 99"
 *
 *     l = Demo.new('Fred')
 *     m = l.method("hello")
 *     m.call   #=> "Hello, @iv = Fred"
 */

VALUE
rb_obj_method(VALUE obj, VALUE vid)
{
    return obj_method(obj, vid, FALSE);
}

/*
 *  call-seq:
 *     obj.public_method(sym)    -> method
 *
 *  Similar to _method_, searches public method only.
 */

VALUE
rb_obj_public_method(VALUE obj, VALUE vid)
{
    return obj_method(obj, vid, TRUE);
}

/*
 *  call-seq:
 *     obj.singleton_method(sym)    -> method
 *
 *  Similar to _method_, searches singleton method only.
 *
 *     class Demo
 *       def initialize(n)
 *         @iv = n
 *       end
 *       def hello()
 *         "Hello, @iv = #{@iv}"
 *       end
 *     end
 *
 *     k = Demo.new(99)
 *     def k.hi
 *       "Hi, @iv = #{@iv}"
 *     end
 *     m = k.singleton_method(:hi)
 *     m.call   #=> "Hi, @iv = 99"
 *     m = k.singleton_method(:hello) #=> NameError
 */

VALUE
rb_obj_singleton_method(VALUE obj, VALUE vid)
{
    const rb_method_entry_t *me;
    VALUE klass;
    ID id = rb_check_id(&vid);

    if (!id) {
	if (!NIL_P(klass = rb_singleton_class_get(obj)) &&
	    respond_to_missing_p(klass, obj, vid, FALSE)) {
	    id = rb_intern_str(vid);
	    return mnew_missing(klass, obj, id, id, rb_cMethod);
	}
      undef:
	rb_name_err_raise("undefined singleton method `%1$s' for `%2$s'",
			  obj, vid);
    }
    if (NIL_P(klass = rb_singleton_class_get(obj)) ||
	UNDEFINED_METHOD_ENTRY_P(me = rb_method_entry_at(klass, id)) ||
	UNDEFINED_REFINED_METHOD_P(me->def)) {
	vid = ID2SYM(id);
	goto undef;
    }
    return mnew_from_me(me, klass, obj, id, rb_cMethod, FALSE);
}

/*
 *  call-seq:
 *     mod.instance_method(symbol)   -> unbound_method
 *
 *  Returns an +UnboundMethod+ representing the given
 *  instance method in _mod_.
 *
 *     class Interpreter
 *       def do_a() print "there, "; end
 *       def do_d() print "Hello ";  end
 *       def do_e() print "!\n";     end
 *       def do_v() print "Dave";    end
 *       Dispatcher = {
 *         "a" => instance_method(:do_a),
 *         "d" => instance_method(:do_d),
 *         "e" => instance_method(:do_e),
 *         "v" => instance_method(:do_v)
 *       }
 *       def interpret(string)
 *         string.each_char {|b| Dispatcher[b].bind(self).call }
 *       end
 *     end
 *
 *     interpreter = Interpreter.new
 *     interpreter.interpret('dave')
 *
 *  <em>produces:</em>
 *
 *     Hello there, Dave!
 */

static VALUE
rb_mod_instance_method(VALUE mod, VALUE vid)
{
    ID id = rb_check_id(&vid);
    if (!id) {
	rb_method_name_error(mod, vid);
    }
    return mnew(mod, Qundef, id, rb_cUnboundMethod, FALSE);
}

/*
 *  call-seq:
 *     mod.public_instance_method(symbol)   -> unbound_method
 *
 *  Similar to _instance_method_, searches public method only.
 */

static VALUE
rb_mod_public_instance_method(VALUE mod, VALUE vid)
{
    ID id = rb_check_id(&vid);
    if (!id) {
	rb_method_name_error(mod, vid);
    }
    return mnew(mod, Qundef, id, rb_cUnboundMethod, TRUE);
}

/*
 *  call-seq:
 *     define_method(symbol, method)     -> symbol
 *     define_method(symbol) { block }   -> symbol
 *
 *  Defines an instance method in the receiver. The _method_
 *  parameter can be a +Proc+, a +Method+ or an +UnboundMethod+ object.
 *  If a block is specified, it is used as the method body. This block
 *  is evaluated using <code>instance_eval</code>, a point that is
 *  tricky to demonstrate because <code>define_method</code> is private.
 *  (This is why we resort to the +send+ hack in this example.)
 *
 *     class A
 *       def fred
 *         puts "In Fred"
 *       end
 *       def create_method(name, &block)
 *         self.class.send(:define_method, name, &block)
 *       end
 *       define_method(:wilma) { puts "Charge it!" }
 *     end
 *     class B < A
 *       define_method(:barney, instance_method(:fred))
 *     end
 *     a = B.new
 *     a.barney
 *     a.wilma
 *     a.create_method(:betty) { p self }
 *     a.betty
 *
 *  <em>produces:</em>
 *
 *     In Fred
 *     Charge it!
 *     #<B:0x401b39e8>
 */

static VALUE
rb_mod_define_method(int argc, VALUE *argv, VALUE mod)
{
    ID id;
    VALUE body;
    VALUE name;
    const rb_cref_t *cref = rb_vm_cref_in_context(mod, mod);
    const rb_scope_visibility_t default_scope_visi = {METHOD_VISI_PUBLIC, FALSE};
    const rb_scope_visibility_t *scope_visi = &default_scope_visi;
    int is_method = FALSE;

    if (cref) {
	scope_visi = CREF_SCOPE_VISI(cref);
    }

    rb_check_arity(argc, 1, 2);
    name = argv[0];
    id = rb_check_id(&name);
    if (argc == 1) {
#if PROC_NEW_REQUIRES_BLOCK
	body = rb_block_lambda();
#else
	rb_thread_t *th = GET_THREAD();
	rb_block_t *block = rb_vm_control_frame_block_ptr(th->cfp);
	if (!block) rb_raise(rb_eArgError, proc_without_block);

	body = block->proc;

	if (SYMBOL_P(body)) {
	    body = rb_sym_to_proc(body);
	}
	else if (!body) {
	    body = rb_vm_make_proc_lambda(th, block, rb_cProc, TRUE);
	}
#endif
    }
    else {
	body = argv[1];

	if (rb_obj_is_method(body)) {
	    is_method = TRUE;
	}
	else if (rb_obj_is_proc(body)) {
	    is_method = FALSE;
	}
	else {
	    rb_raise(rb_eTypeError,
		     "wrong argument type %s (expected Proc/Method)",
		     rb_obj_classname(body));
	}
    }
    if (!id) id = rb_to_id(name);

    if (is_method) {
	struct METHOD *method = (struct METHOD *)DATA_PTR(body);
	if (method->me->owner != mod && !RB_TYPE_P(method->me->owner, T_MODULE) &&
	    !RTEST(rb_class_inherited_p(mod, method->me->owner))) {
	    if (FL_TEST(method->me->owner, FL_SINGLETON)) {
		rb_raise(rb_eTypeError,
			 "can't bind singleton method to a different class");
	    }
	    else {
		rb_raise(rb_eTypeError,
			 "bind argument must be a subclass of % "PRIsVALUE,
			 rb_class_name(method->me->owner));
	    }
	}
	rb_method_entry_set(mod, id, method->me, scope_visi->method_visi);
	if (scope_visi->module_func) {
	    rb_method_entry_set(rb_singleton_class(mod), id, method->me, METHOD_VISI_PUBLIC);
	}
	RB_GC_GUARD(body);
    }
    else {
	rb_proc_t *proc;
	body = proc_dup(body);
	GetProcPtr(body, proc);
	if (RUBY_VM_NORMAL_ISEQ_P(proc->block.iseq)) {
	    proc->is_lambda = TRUE;
	    proc->is_from_method = TRUE;
	}
	rb_add_method(mod, id, VM_METHOD_TYPE_BMETHOD, (void *)body, scope_visi->method_visi);
	if (scope_visi->module_func) {
	    rb_add_method(rb_singleton_class(mod), id, VM_METHOD_TYPE_BMETHOD, (void *)body, METHOD_VISI_PUBLIC);
	}
    }

    return ID2SYM(id);
}

/*
 *  call-seq:
 *     define_singleton_method(symbol, method) -> new_method
 *     define_singleton_method(symbol) { block } -> proc
 *
 *  Defines a singleton method in the receiver. The _method_
 *  parameter can be a +Proc+, a +Method+ or an +UnboundMethod+ object.
 *  If a block is specified, it is used as the method body.
 *
 *     class A
 *       class << self
 *         def class_name
 *           to_s
 *         end
 *       end
 *     end
 *     A.define_singleton_method(:who_am_i) do
 *       "I am: #{class_name}"
 *     end
 *     A.who_am_i   # ==> "I am: A"
 *
 *     guy = "Bob"
 *     guy.define_singleton_method(:hello) { "#{self}: Hello there!" }
 *     guy.hello    #=>  "Bob: Hello there!"
 */

static VALUE
rb_obj_define_method(int argc, VALUE *argv, VALUE obj)
{
    VALUE klass = rb_singleton_class(obj);

    return rb_mod_define_method(argc, argv, klass);
}

/*
 *     define_method(symbol, method)     -> new_method
 *     define_method(symbol) { block }   -> proc
 *
 *  Defines a global function by _method_ or the block.
 */

static VALUE
top_define_method(int argc, VALUE *argv, VALUE obj)
{
    rb_thread_t *th = GET_THREAD();
    VALUE klass;

    klass = th->top_wrapper;
    if (klass) {
	rb_warning("main.define_method in the wrapped load is effective only in wrapper module");
    }
    else {
	klass = rb_cObject;
    }
    return rb_mod_define_method(argc, argv, klass);
}

/*
 *  call-seq:
 *    method.clone -> new_method
 *
 *  Returns a clone of this method.
 *
 *    class A
 *      def foo
 *        return "bar"
 *      end
 *    end
 *
 *    m = A.new.method(:foo)
 *    m.call # => "bar"
 *    n = m.clone.call # => "bar"
 */

static VALUE
method_clone(VALUE self)
{
    VALUE clone;
    struct METHOD *orig, *data;

    TypedData_Get_Struct(self, struct METHOD, &method_data_type, orig);
    clone = TypedData_Make_Struct(CLASS_OF(self), struct METHOD, &method_data_type, data);
    CLONESETUP(clone, self);
    RB_OBJ_WRITE(clone, &data->recv, orig->recv);
    RB_OBJ_WRITE(clone, &data->klass, orig->klass);
    RB_OBJ_WRITE(clone, &data->me, rb_method_entry_clone(orig->me));
    return clone;
}

/*
 *  call-seq:
 *     meth.call(args, ...)    -> obj
 *     meth[args, ...]         -> obj
 *
 *  Invokes the <i>meth</i> with the specified arguments, returning the
 *  method's return value.
 *
 *     m = 12.method("+")
 *     m.call(3)    #=> 15
 *     m.call(20)   #=> 32
 */

VALUE
rb_method_call(int argc, const VALUE *argv, VALUE method)
{
    VALUE proc = rb_block_given_p() ? rb_block_proc() : Qnil;
    return rb_method_call_with_block(argc, argv, method, proc);
}

static const rb_callable_method_entry_t *
method_callable_method_entry(struct METHOD *data)
{
    if (data->me->defined_class == 0) rb_bug("method_callable_method_entry: not callable.");
    return (const rb_callable_method_entry_t *)data->me;
}

VALUE
rb_method_call_with_block(int argc, const VALUE *argv, VALUE method, VALUE pass_procval)
{
    VALUE result = Qnil;	/* OK */
    struct METHOD *data;
    int state;
    volatile int safe = -1;

    TypedData_Get_Struct(method, struct METHOD, &method_data_type, data);
    if (data->recv == Qundef) {
	rb_raise(rb_eTypeError, "can't call unbound method; bind first");
    }
    PUSH_TAG();
    if (OBJ_TAINTED(method)) {
	const int safe_level_to_run = RUBY_SAFE_LEVEL_MAX;
	safe = rb_safe_level();
	if (safe < safe_level_to_run) {
	    rb_set_safe_level_force(safe_level_to_run);
	}
    }
    if ((state = EXEC_TAG()) == 0) {
	rb_thread_t *th = GET_THREAD();
	rb_block_t *block = 0;

	if (!NIL_P(pass_procval)) {
	    rb_proc_t *pass_proc;
	    GetProcPtr(pass_procval, pass_proc);
	    block = &pass_proc->block;
	}

	th->passed_block = block;
	VAR_INITIALIZED(data);
	result = rb_vm_call(th, data->recv, data->me->called_id, argc, argv, method_callable_method_entry(data));
    }
    POP_TAG();
    if (safe >= 0)
	rb_set_safe_level_force(safe);
    if (state)
	JUMP_TAG(state);
    return result;
}

/**********************************************************************
 *
 * Document-class: UnboundMethod
 *
 *  Ruby supports two forms of objectified methods. Class
 *  <code>Method</code> is used to represent methods that are associated
 *  with a particular object: these method objects are bound to that
 *  object. Bound method objects for an object can be created using
 *  <code>Object#method</code>.
 *
 *  Ruby also supports unbound methods; methods objects that are not
 *  associated with a particular object. These can be created either by
 *  calling <code>Module#instance_method</code> or by calling
 *  <code>unbind</code> on a bound method object. The result of both of
 *  these is an <code>UnboundMethod</code> object.
 *
 *  Unbound methods can only be called after they are bound to an
 *  object. That object must be a kind_of? the method's original
 *  class.
 *
 *     class Square
 *       def area
 *         @side * @side
 *       end
 *       def initialize(side)
 *         @side = side
 *       end
 *     end
 *
 *     area_un = Square.instance_method(:area)
 *
 *     s = Square.new(12)
 *     area = area_un.bind(s)
 *     area.call   #=> 144
 *
 *  Unbound methods are a reference to the method at the time it was
 *  objectified: subsequent changes to the underlying class will not
 *  affect the unbound method.
 *
 *     class Test
 *       def test
 *         :original
 *       end
 *     end
 *     um = Test.instance_method(:test)
 *     class Test
 *       def test
 *         :modified
 *       end
 *     end
 *     t = Test.new
 *     t.test            #=> :modified
 *     um.bind(t).call   #=> :original
 *
 */

/*
 *  call-seq:
 *     umeth.bind(obj) -> method
 *
 *  Bind <i>umeth</i> to <i>obj</i>. If <code>Klass</code> was the class
 *  from which <i>umeth</i> was obtained,
 *  <code>obj.kind_of?(Klass)</code> must be true.
 *
 *     class A
 *       def test
 *         puts "In test, class = #{self.class}"
 *       end
 *     end
 *     class B < A
 *     end
 *     class C < B
 *     end
 *
 *
 *     um = B.instance_method(:test)
 *     bm = um.bind(C.new)
 *     bm.call
 *     bm = um.bind(B.new)
 *     bm.call
 *     bm = um.bind(A.new)
 *     bm.call
 *
 *  <em>produces:</em>
 *
 *     In test, class = C
 *     In test, class = B
 *     prog.rb:16:in `bind': bind argument must be an instance of B (TypeError)
 *     	from prog.rb:16
 */

static VALUE
umethod_bind(VALUE method, VALUE recv)
{
    struct METHOD *data, *bound;
    VALUE methclass, klass;

    TypedData_Get_Struct(method, struct METHOD, &method_data_type, data);

    methclass = data->me->owner;

    if (!RB_TYPE_P(methclass, T_MODULE) &&
	methclass != CLASS_OF(recv) && !rb_obj_is_kind_of(recv, methclass)) {
	if (FL_TEST(methclass, FL_SINGLETON)) {
	    rb_raise(rb_eTypeError,
		     "singleton method called for a different object");
	}
	else {
	    rb_raise(rb_eTypeError, "bind argument must be an instance of % "PRIsVALUE,
		     rb_class_name(methclass));
	}
    }

    klass  = CLASS_OF(recv);

    method = TypedData_Make_Struct(rb_cMethod, struct METHOD, &method_data_type, bound);
    RB_OBJ_WRITE(method, &bound->recv, recv);
    RB_OBJ_WRITE(method, &bound->klass, data->klass);
    RB_OBJ_WRITE(method, &bound->me, rb_method_entry_clone(data->me));

    if (RB_TYPE_P(bound->me->owner, T_MODULE)) {
	VALUE ic = rb_class_search_ancestor(klass, bound->me->owner);
	if (ic) {
	    klass = ic;
	}
	else {
	    klass = rb_include_class_new(methclass, klass);
	}
	RB_OBJ_WRITE(method, &bound->me, rb_method_entry_complement_defined_class(bound->me, klass));
    }

    return method;
}

/*
 * Returns the number of required parameters and stores the maximum
 * number of parameters in max, or UNLIMITED_ARGUMENTS
 * if there is no maximum.
 */
static int
rb_method_entry_min_max_arity(const rb_method_entry_t *me, int *max)
{
    const rb_method_definition_t *def = me->def;

    if (!def) return *max = 0;
    switch (def->type) {
      case VM_METHOD_TYPE_CFUNC:
	if (def->body.cfunc.argc < 0) {
	    *max = UNLIMITED_ARGUMENTS;
	    return 0;
	}
	return *max = check_argc(def->body.cfunc.argc);
      case VM_METHOD_TYPE_ZSUPER:
	*max = UNLIMITED_ARGUMENTS;
	return 0;
      case VM_METHOD_TYPE_ATTRSET:
	return *max = 1;
      case VM_METHOD_TYPE_IVAR:
	return *max = 0;
      case VM_METHOD_TYPE_ALIAS:
	return rb_method_entry_min_max_arity(def->body.alias.original_me, max);
      case VM_METHOD_TYPE_BMETHOD:
	return rb_proc_min_max_arity(def->body.proc, max);
      case VM_METHOD_TYPE_ISEQ: {
	const rb_iseq_t *iseq = rb_iseq_check(def->body.iseq.iseqptr);
	return rb_iseq_min_max_arity(iseq, max);
      }
      case VM_METHOD_TYPE_UNDEF:
      case VM_METHOD_TYPE_NOTIMPLEMENTED:
	return *max = 0;
      case VM_METHOD_TYPE_MISSING:
	*max = UNLIMITED_ARGUMENTS;
	return 0;
      case VM_METHOD_TYPE_OPTIMIZED: {
	switch (def->body.optimize_type) {
	  case OPTIMIZED_METHOD_TYPE_SEND:
	    *max = UNLIMITED_ARGUMENTS;
	    return 0;
	  case OPTIMIZED_METHOD_TYPE_CALL:
	    *max = UNLIMITED_ARGUMENTS;
	    return 0;
	  default:
	    break;
	}
	break;
      }
      case VM_METHOD_TYPE_REFINED:
	*max = UNLIMITED_ARGUMENTS;
	return 0;
    }
    rb_bug("rb_method_entry_min_max_arity: invalid method entry type (%d)", def->type);
    UNREACHABLE;
}

int
rb_method_entry_arity(const rb_method_entry_t *me)
{
    int max, min = rb_method_entry_min_max_arity(me, &max);
    return min == max ? min : -min-1;
}

/*
 *  call-seq:
 *     meth.arity    -> fixnum
 *
 *  Returns an indication of the number of arguments accepted by a
 *  method. Returns a nonnegative integer for methods that take a fixed
 *  number of arguments. For Ruby methods that take a variable number of
 *  arguments, returns -n-1, where n is the number of required
 *  arguments. For methods written in C, returns -1 if the call takes a
 *  variable number of arguments.
 *
 *     class C
 *       def one;    end
 *       def two(a); end
 *       def three(*a);  end
 *       def four(a, b); end
 *       def five(a, b, *c);    end
 *       def six(a, b, *c, &d); end
 *     end
 *     c = C.new
 *     c.method(:one).arity     #=> 0
 *     c.method(:two).arity     #=> 1
 *     c.method(:three).arity   #=> -1
 *     c.method(:four).arity    #=> 2
 *     c.method(:five).arity    #=> -3
 *     c.method(:six).arity     #=> -3
 *
 *     "cat".method(:size).arity      #=> 0
 *     "cat".method(:replace).arity   #=> 1
 *     "cat".method(:squeeze).arity   #=> -1
 *     "cat".method(:count).arity     #=> -1
 */

static VALUE
method_arity_m(VALUE method)
{
    int n = method_arity(method);
    return INT2FIX(n);
}

static int
method_arity(VALUE method)
{
    struct METHOD *data;

    TypedData_Get_Struct(method, struct METHOD, &method_data_type, data);
    return rb_method_entry_arity(data->me);
}

static const rb_method_entry_t *
original_method_entry(VALUE mod, ID id)
{
    const rb_method_entry_t *me;

    while ((me = rb_method_entry(mod, id)) != 0) {
	const rb_method_definition_t *def = me->def;
	if (def->type != VM_METHOD_TYPE_ZSUPER) break;
	mod = RCLASS_SUPER(me->owner);
	id = def->original_id;
    }
    return me;
}

static int
method_min_max_arity(VALUE method, int *max)
{
    const struct METHOD *data;

    TypedData_Get_Struct(method, struct METHOD, &method_data_type, data);
    return rb_method_entry_min_max_arity(data->me, max);
}

int
rb_mod_method_arity(VALUE mod, ID id)
{
    const rb_method_entry_t *me = original_method_entry(mod, id);
    if (!me) return 0;		/* should raise? */
    return rb_method_entry_arity(me);
}

int
rb_obj_method_arity(VALUE obj, ID id)
{
    return rb_mod_method_arity(CLASS_OF(obj), id);
}

static inline const rb_method_definition_t *
method_def(VALUE method)
{
    const struct METHOD *data;

    TypedData_Get_Struct(method, struct METHOD, &method_data_type, data);
    return data->me->def;
}

static const rb_iseq_t *
method_def_iseq(const rb_method_definition_t *def)
{
    switch (def->type) {
      case VM_METHOD_TYPE_ISEQ:
	return rb_iseq_check(def->body.iseq.iseqptr);
      case VM_METHOD_TYPE_BMETHOD:
	return rb_proc_get_iseq(def->body.proc, 0);
      case VM_METHOD_TYPE_ALIAS:
	return method_def_iseq(def->body.alias.original_me->def);
      case VM_METHOD_TYPE_CFUNC:
      case VM_METHOD_TYPE_ATTRSET:
      case VM_METHOD_TYPE_IVAR:
      case VM_METHOD_TYPE_ZSUPER:
      case VM_METHOD_TYPE_UNDEF:
      case VM_METHOD_TYPE_NOTIMPLEMENTED:
      case VM_METHOD_TYPE_OPTIMIZED:
      case VM_METHOD_TYPE_MISSING:
      case VM_METHOD_TYPE_REFINED:
	break;
    }
    return NULL;
}

const rb_iseq_t *
rb_method_iseq(VALUE method)
{
    return method_def_iseq(method_def(method));
}

static const rb_cref_t *
method_cref(VALUE method)
{
    const rb_method_definition_t *def = method_def(method);

  again:
    switch (def->type) {
      case VM_METHOD_TYPE_ISEQ:
	return def->body.iseq.cref;
      case VM_METHOD_TYPE_ALIAS:
	def = def->body.alias.original_me->def;
	goto again;
      default:
	return NULL;
    }
}

static VALUE
method_def_location(const rb_method_definition_t *def)
{
    if (def->type == VM_METHOD_TYPE_ATTRSET || def->type == VM_METHOD_TYPE_IVAR) {
	if (!def->body.attr.location)
	    return Qnil;
	return rb_ary_dup(def->body.attr.location);
    }
    return iseq_location(method_def_iseq(def));
}

VALUE
rb_method_entry_location(const rb_method_entry_t *me)
{
    if (!me) return Qnil;
    return method_def_location(me->def);
}

VALUE
rb_mod_method_location(VALUE mod, ID id)
{
    const rb_method_entry_t *me = original_method_entry(mod, id);
    return rb_method_entry_location(me);
}

VALUE
rb_obj_method_location(VALUE obj, ID id)
{
    return rb_mod_method_location(CLASS_OF(obj), id);
}

/*
 * call-seq:
 *    meth.source_location  -> [String, Fixnum]
 *
 * Returns the Ruby source filename and line number containing this method
 * or nil if this method was not defined in Ruby (i.e. native)
 */

VALUE
rb_method_location(VALUE method)
{
    return method_def_location(method_def(method));
}

/*
 * call-seq:
 *    meth.parameters  -> array
 *
 * Returns the parameter information of this method.
 *
 *    def foo(bar); end
 *    method(:foo).parameters #=> [[:req, :bar]]
 *
 *    def foo(bar, baz, bat, &blk); end
 *    method(:foo).parameters #=> [[:req, :bar], [:req, :baz], [:req, :bat], [:block, :blk]]
 *
 *    def foo(bar, *args); end
 *    method(:foo).parameters #=> [[:req, :bar], [:rest, :args]]
 *
 *    def foo(bar, baz, *args, &blk); end
 *    method(:foo).parameters #=> [[:req, :bar], [:req, :baz], [:rest, :args], [:block, :blk]]
 */

static VALUE
rb_method_parameters(VALUE method)
{
    const rb_iseq_t *iseq = rb_method_iseq(method);
    if (!iseq) {
	return unnamed_parameters(method_arity(method));
    }
    return rb_iseq_parameters(iseq, 0);
}

/*
 *  call-seq:
 *   meth.to_s      ->  string
 *   meth.inspect   ->  string
 *
 *  Returns the name of the underlying method.
 *
 *    "cat".method(:count).inspect   #=> "#<Method: String#count>"
 */

static VALUE
method_inspect(VALUE method)
{
    struct METHOD *data;
    VALUE str;
    const char *s;
    const char *sharp = "#";
    VALUE mklass;
    VALUE defined_class;

    TypedData_Get_Struct(method, struct METHOD, &method_data_type, data);
    str = rb_str_buf_new2("#<");
    s = rb_obj_classname(method);
    rb_str_buf_cat2(str, s);
    rb_str_buf_cat2(str, ": ");

    mklass = data->klass;

    if (data->me->def->type == VM_METHOD_TYPE_ALIAS) {
	defined_class = data->me->def->body.alias.original_me->owner;
    }
    else {
	defined_class = method_entry_defined_class(data->me);
    }

    if (RB_TYPE_P(defined_class, T_ICLASS)) {
	defined_class = RBASIC_CLASS(defined_class);
    }

    if (FL_TEST(mklass, FL_SINGLETON)) {
	VALUE v = rb_ivar_get(mklass, attached);

	if (data->recv == Qundef) {
	    rb_str_buf_append(str, rb_inspect(mklass));
	}
	else if (data->recv == v) {
	    rb_str_buf_append(str, rb_inspect(v));
	    sharp = ".";
	}
	else {
	    rb_str_buf_append(str, rb_inspect(data->recv));
	    rb_str_buf_cat2(str, "(");
	    rb_str_buf_append(str, rb_inspect(v));
	    rb_str_buf_cat2(str, ")");
	    sharp = ".";
	}
    }
    else {
	rb_str_buf_append(str, rb_class_name(mklass));
	if (defined_class != mklass) {
	    rb_str_buf_cat2(str, "(");
	    rb_str_buf_append(str, rb_class_name(defined_class));
	    rb_str_buf_cat2(str, ")");
	}
    }
    rb_str_buf_cat2(str, sharp);
    rb_str_append(str, rb_id2str(data->me->called_id));
    if (data->me->called_id != data->me->def->original_id) {
	rb_str_catf(str, "(%"PRIsVALUE")",
		    rb_id2str(data->me->def->original_id));
    }
    if (data->me->def->type == VM_METHOD_TYPE_NOTIMPLEMENTED) {
        rb_str_buf_cat2(str, " (not-implemented)");
    }
    rb_str_buf_cat2(str, ">");

    return str;
}

static VALUE
mproc(VALUE method)
{
    return rb_funcallv(rb_mRubyVMFrozenCore, idProc, 0, 0);
}

static VALUE
mlambda(VALUE method)
{
    return rb_funcallv(rb_mRubyVMFrozenCore, idLambda, 0, 0);
}

static VALUE
bmcall(VALUE args, VALUE method, int argc, VALUE *argv, VALUE passed_proc)
{
    volatile VALUE a;
    VALUE ret;

    if (CLASS_OF(args) != rb_cArray) {
	args = rb_ary_new3(1, args);
	argc = 1;
    }
    else {
	argc = check_argc(RARRAY_LEN(args));
    }
    ret = rb_method_call_with_block(argc, RARRAY_PTR(args), method, passed_proc);
    RB_GC_GUARD(a) = args;
    return ret;
}

VALUE
rb_proc_new(
    VALUE (*func)(ANYARGS), /* VALUE yieldarg[, VALUE procarg] */
    VALUE val)
{
    VALUE procval = rb_iterate(mproc, 0, func, val);
    return procval;
}

/*
 *  call-seq:
 *     meth.to_proc    -> proc
 *
 *  Returns a <code>Proc</code> object corresponding to this method.
 */

static VALUE
method_to_proc(VALUE method)
{
    VALUE procval;
    rb_proc_t *proc;

    /*
     * class Method
     *   def to_proc
     *     lambda{|*args|
     *       self.call(*args)
     *     }
     *   end
     * end
     */
    procval = rb_iterate(mlambda, 0, bmcall, method);
    GetProcPtr(procval, proc);
    proc->is_from_method = 1;
    return procval;
}

/*
 * call-seq:
 *   meth.super_method  -> method
 *
 * Returns a Method of superclass which would be called when super is used
 * or nil if there is no method on superclass.
 */

static VALUE
method_super_method(VALUE method)
{
    const struct METHOD *data;
    VALUE super_class;
    const rb_method_entry_t *me;

    TypedData_Get_Struct(method, struct METHOD, &method_data_type, data);
    super_class = RCLASS_SUPER(method_entry_defined_class(data->me));
    if (!super_class) return Qnil;
    me = (rb_method_entry_t *)rb_callable_method_entry_without_refinements(super_class, data->me->called_id);
    if (!me) return Qnil;
    return mnew_internal(me, super_class, data->recv, data->me->called_id, rb_obj_class(method), FALSE, FALSE);
}

/*
 * call-seq:
 *   local_jump_error.exit_value  -> obj
 *
 * Returns the exit value associated with this +LocalJumpError+.
 */
static VALUE
localjump_xvalue(VALUE exc)
{
    return rb_iv_get(exc, "@exit_value");
}

/*
 * call-seq:
 *    local_jump_error.reason   -> symbol
 *
 * The reason this block was terminated:
 * :break, :redo, :retry, :next, :return, or :noreason.
 */

static VALUE
localjump_reason(VALUE exc)
{
    return rb_iv_get(exc, "@reason");
}

rb_cref_t *rb_vm_cref_new_toplevel(void); /* vm.c */

static VALUE
env_clone(VALUE envval, VALUE receiver, const rb_cref_t *cref)
{
    VALUE newenvval = TypedData_Wrap_Struct(RBASIC_CLASS(envval), RTYPEDDATA_TYPE(envval), 0);
    rb_env_t *env, *newenv;
    int envsize;

    if (cref == NULL) {
	cref = rb_vm_cref_new_toplevel();
    }

    GetEnvPtr(envval, env);
    envsize = sizeof(rb_env_t) + (env->env_size - 1) * sizeof(VALUE);
    newenv = xmalloc(envsize);
    memcpy(newenv, env, envsize);
    RTYPEDDATA_DATA(newenvval) = newenv;
    newenv->block.self = receiver;
    newenv->block.ep[-1] = (VALUE)cref;
    return newenvval;
}

/*
 *  call-seq:
 *     prc.binding    -> binding
 *
 *  Returns the binding associated with <i>prc</i>. Note that
 *  <code>Kernel#eval</code> accepts either a <code>Proc</code> or a
 *  <code>Binding</code> object as its second parameter.
 *
 *     def fred(param)
 *       proc {}
 *     end
 *
 *     b = fred(99)
 *     eval("param", b.binding)   #=> 99
 */
static VALUE
proc_binding(VALUE self)
{
    VALUE bindval, envval;
    const rb_proc_t *proc;
    const rb_iseq_t *iseq;
    rb_binding_t *bind;

    GetProcPtr(self, proc);
    envval = rb_vm_proc_envval(proc);
    iseq = proc->block.iseq;
    if (SYMBOL_P(iseq)) goto error;
    if (RUBY_VM_IFUNC_P(iseq)) {
	struct vm_ifunc *ifunc = (struct vm_ifunc *)iseq;
	if (IS_METHOD_PROC_IFUNC(ifunc)) {
	    VALUE method = (VALUE)ifunc->data;
	    envval = env_clone(envval, method_receiver(method), method_cref(method));
	    iseq = rb_method_iseq(method);
	}
	else {
	  error:
	    rb_raise(rb_eArgError, "Can't create Binding from C level Proc");
	}
    }

    bindval = rb_binding_alloc(rb_cBinding);
    GetBindingPtr(bindval, bind);
    bind->env = envval;

    if (iseq) {
	rb_iseq_check(iseq);
	bind->path = iseq->body->location.path;
	bind->first_lineno = FIX2INT(rb_iseq_first_lineno(iseq));
    }
    else {
	bind->path = Qnil;
	bind->first_lineno = 0;
    }

    return bindval;
}

static VALUE curry(VALUE dummy, VALUE args, int argc, VALUE *argv, VALUE passed_proc);

static VALUE
make_curry_proc(VALUE proc, VALUE passed, VALUE arity)
{
    VALUE args = rb_ary_new3(3, proc, passed, arity);
    rb_proc_t *procp;
    int is_lambda;

    GetProcPtr(proc, procp);
    is_lambda = procp->is_lambda;
    rb_ary_freeze(passed);
    rb_ary_freeze(args);
    proc = rb_proc_new(curry, args);
    GetProcPtr(proc, procp);
    procp->is_lambda = is_lambda;
    return proc;
}

static VALUE
curry(VALUE dummy, VALUE args, int argc, VALUE *argv, VALUE passed_proc)
{
    VALUE proc, passed, arity;
    proc = RARRAY_AREF(args, 0);
    passed = RARRAY_AREF(args, 1);
    arity = RARRAY_AREF(args, 2);

    passed = rb_ary_plus(passed, rb_ary_new4(argc, argv));
    rb_ary_freeze(passed);

    if (RARRAY_LEN(passed) < FIX2INT(arity)) {
	if (!NIL_P(passed_proc)) {
	    rb_warn("given block not used");
	}
	arity = make_curry_proc(proc, passed, arity);
	return arity;
    }
    else {
	return rb_proc_call_with_block(proc, check_argc(RARRAY_LEN(passed)), RARRAY_CONST_PTR(passed), passed_proc);
    }
}

 /*
  *  call-seq:
  *     prc.curry         -> a_proc
  *     prc.curry(arity)  -> a_proc
  *
  *  Returns a curried proc. If the optional <i>arity</i> argument is given,
  *  it determines the number of arguments.
  *  A curried proc receives some arguments. If a sufficient number of
  *  arguments are supplied, it passes the supplied arguments to the original
  *  proc and returns the result. Otherwise, returns another curried proc that
  *  takes the rest of arguments.
  *
  *     b = proc {|x, y, z| (x||0) + (y||0) + (z||0) }
  *     p b.curry[1][2][3]           #=> 6
  *     p b.curry[1, 2][3, 4]        #=> 6
  *     p b.curry(5)[1][2][3][4][5]  #=> 6
  *     p b.curry(5)[1, 2][3, 4][5]  #=> 6
  *     p b.curry(1)[1]              #=> 1
  *
  *     b = proc {|x, y, z, *w| (x||0) + (y||0) + (z||0) + w.inject(0, &:+) }
  *     p b.curry[1][2][3]           #=> 6
  *     p b.curry[1, 2][3, 4]        #=> 10
  *     p b.curry(5)[1][2][3][4][5]  #=> 15
  *     p b.curry(5)[1, 2][3, 4][5]  #=> 15
  *     p b.curry(1)[1]              #=> 1
  *
  *     b = lambda {|x, y, z| (x||0) + (y||0) + (z||0) }
  *     p b.curry[1][2][3]           #=> 6
  *     p b.curry[1, 2][3, 4]        #=> wrong number of arguments (given 4, expected 3)
  *     p b.curry(5)                 #=> wrong number of arguments (given 5, expected 3)
  *     p b.curry(1)                 #=> wrong number of arguments (given 1, expected 3)
  *
  *     b = lambda {|x, y, z, *w| (x||0) + (y||0) + (z||0) + w.inject(0, &:+) }
  *     p b.curry[1][2][3]           #=> 6
  *     p b.curry[1, 2][3, 4]        #=> 10
  *     p b.curry(5)[1][2][3][4][5]  #=> 15
  *     p b.curry(5)[1, 2][3, 4][5]  #=> 15
  *     p b.curry(1)                 #=> wrong number of arguments (given 1, expected 3)
  *
  *     b = proc { :foo }
  *     p b.curry[]                  #=> :foo
  */
static VALUE
proc_curry(int argc, const VALUE *argv, VALUE self)
{
    int sarity, max_arity, min_arity = rb_proc_min_max_arity(self, &max_arity);
    VALUE arity;

    rb_scan_args(argc, argv, "01", &arity);
    if (NIL_P(arity)) {
	arity = INT2FIX(min_arity);
    }
    else {
	sarity = FIX2INT(arity);
	if (rb_proc_lambda_p(self)) {
	    rb_check_arity(sarity, min_arity, max_arity);
	}
    }

    return make_curry_proc(self, rb_ary_new(), arity);
}

/*
 *  call-seq:
 *     meth.curry        -> proc
 *     meth.curry(arity) -> proc
 *
 *  Returns a curried proc based on the method. When the proc is called with a number of
 *  arguments that is lower than the method's arity, then another curried proc is returned.
 *  Only when enough arguments have been supplied to satisfy the method signature, will the
 *  method actually be called.
 *
 *  The optional <i>arity</i> argument should be supplied when currying methods with
 *  variable arguments to determine how many arguments are needed before the method is
 *  called.
 *
 *     def foo(a,b,c)
 *       [a, b, c]
 *     end
 *
 *     proc  = self.method(:foo).curry
 *     proc2 = proc.call(1, 2)          #=> #<Proc>
 *     proc2.call(3)                    #=> [1,2,3]
 *
 *     def vararg(*args)
 *       args
 *     end
 *
 *     proc = self.method(:vararg).curry(4)
 *     proc2 = proc.call(:x)      #=> #<Proc>
 *     proc3 = proc2.call(:y, :z) #=> #<Proc>
 *     proc3.call(:a)             #=> [:x, :y, :z, :a]
 */

static VALUE
rb_method_curry(int argc, const VALUE *argv, VALUE self)
{
    VALUE proc = method_to_proc(self);
    return proc_curry(argc, argv, proc);
}

/*
 *  Document-class: LocalJumpError
 *
 *  Raised when Ruby can't yield as requested.
 *
 *  A typical scenario is attempting to yield when no block is given:
 *
 *     def call_block
 *       yield 42
 *     end
 *     call_block
 *
 *  <em>raises the exception:</em>
 *
 *     LocalJumpError: no block given (yield)
 *
 *  A more subtle example:
 *
 *     def get_me_a_return
 *       Proc.new { return 42 }
 *     end
 *     get_me_a_return.call
 *
 *  <em>raises the exception:</em>
 *
 *     LocalJumpError: unexpected return
 */

/*
 *  Document-class: SystemStackError
 *
 *  Raised in case of a stack overflow.
 *
 *     def me_myself_and_i
 *       me_myself_and_i
 *     end
 *     me_myself_and_i
 *
 *  <em>raises the exception:</em>
 *
 *    SystemStackError: stack level too deep
 */

/*
 *  <code>Proc</code> objects are blocks of code that have been bound to
 *  a set of local variables. Once bound, the code may be called in
 *  different contexts and still access those variables.
 *
 *     def gen_times(factor)
 *       return Proc.new {|n| n*factor }
 *     end
 *
 *     times3 = gen_times(3)
 *     times5 = gen_times(5)
 *
 *     times3.call(12)               #=> 36
 *     times5.call(5)                #=> 25
 *     times3.call(times5.call(4))   #=> 60
 *
 */

void
Init_Proc(void)
{
    /* Proc */
    rb_cProc = rb_define_class("Proc", rb_cObject);
    rb_undef_alloc_func(rb_cProc);
    rb_define_singleton_method(rb_cProc, "new", rb_proc_s_new, -1);

    rb_add_method(rb_cProc, rb_intern("call"), VM_METHOD_TYPE_OPTIMIZED,
		  (void *)OPTIMIZED_METHOD_TYPE_CALL, METHOD_VISI_PUBLIC);
    rb_add_method(rb_cProc, rb_intern("[]"), VM_METHOD_TYPE_OPTIMIZED,
		  (void *)OPTIMIZED_METHOD_TYPE_CALL, METHOD_VISI_PUBLIC);
    rb_add_method(rb_cProc, rb_intern("==="), VM_METHOD_TYPE_OPTIMIZED,
		  (void *)OPTIMIZED_METHOD_TYPE_CALL, METHOD_VISI_PUBLIC);
    rb_add_method(rb_cProc, rb_intern("yield"), VM_METHOD_TYPE_OPTIMIZED,
		  (void *)OPTIMIZED_METHOD_TYPE_CALL, METHOD_VISI_PUBLIC);

    rb_define_method(rb_cProc, "to_proc", proc_to_proc, 0);
    rb_define_method(rb_cProc, "arity", proc_arity, 0);
    rb_define_method(rb_cProc, "clone", proc_clone, 0);
    rb_define_method(rb_cProc, "dup", proc_dup, 0);
    rb_define_method(rb_cProc, "hash", proc_hash, 0);
    rb_define_method(rb_cProc, "to_s", proc_to_s, 0);
    rb_define_alias(rb_cProc, "inspect", "to_s");
    rb_define_method(rb_cProc, "lambda?", rb_proc_lambda_p, 0);
    rb_define_method(rb_cProc, "binding", proc_binding, 0);
    rb_define_method(rb_cProc, "curry", proc_curry, -1);
    rb_define_method(rb_cProc, "source_location", rb_proc_location, 0);
    rb_define_method(rb_cProc, "parameters", rb_proc_parameters, 0);

    /* Exceptions */
    rb_eLocalJumpError = rb_define_class("LocalJumpError", rb_eStandardError);
    rb_define_method(rb_eLocalJumpError, "exit_value", localjump_xvalue, 0);
    rb_define_method(rb_eLocalJumpError, "reason", localjump_reason, 0);

    rb_eSysStackError = rb_define_class("SystemStackError", rb_eException);
    rb_vm_register_special_exception(ruby_error_sysstack, rb_eSysStackError, "stack level too deep");

    /* utility functions */
    rb_define_global_function("proc", rb_block_proc, 0);
    rb_define_global_function("lambda", rb_block_lambda, 0);

    /* Method */
    rb_cMethod = rb_define_class("Method", rb_cObject);
    rb_undef_alloc_func(rb_cMethod);
    rb_undef_method(CLASS_OF(rb_cMethod), "new");
    rb_define_method(rb_cMethod, "==", method_eq, 1);
    rb_define_method(rb_cMethod, "eql?", method_eq, 1);
    rb_define_method(rb_cMethod, "hash", method_hash, 0);
    rb_define_method(rb_cMethod, "clone", method_clone, 0);
    rb_define_method(rb_cMethod, "call", rb_method_call, -1);
    rb_define_method(rb_cMethod, "curry", rb_method_curry, -1);
    rb_define_method(rb_cMethod, "[]", rb_method_call, -1);
    rb_define_method(rb_cMethod, "arity", method_arity_m, 0);
    rb_define_method(rb_cMethod, "inspect", method_inspect, 0);
    rb_define_method(rb_cMethod, "to_s", method_inspect, 0);
    rb_define_method(rb_cMethod, "to_proc", method_to_proc, 0);
    rb_define_method(rb_cMethod, "receiver", method_receiver, 0);
    rb_define_method(rb_cMethod, "name", method_name, 0);
    rb_define_method(rb_cMethod, "original_name", method_original_name, 0);
    rb_define_method(rb_cMethod, "owner", method_owner, 0);
    rb_define_method(rb_cMethod, "unbind", method_unbind, 0);
    rb_define_method(rb_cMethod, "source_location", rb_method_location, 0);
    rb_define_method(rb_cMethod, "parameters", rb_method_parameters, 0);
    rb_define_method(rb_cMethod, "super_method", method_super_method, 0);
    rb_define_method(rb_mKernel, "method", rb_obj_method, 1);
    rb_define_method(rb_mKernel, "public_method", rb_obj_public_method, 1);
    rb_define_method(rb_mKernel, "singleton_method", rb_obj_singleton_method, 1);

    /* UnboundMethod */
    rb_cUnboundMethod = rb_define_class("UnboundMethod", rb_cObject);
    rb_undef_alloc_func(rb_cUnboundMethod);
    rb_undef_method(CLASS_OF(rb_cUnboundMethod), "new");
    rb_define_method(rb_cUnboundMethod, "==", method_eq, 1);
    rb_define_method(rb_cUnboundMethod, "eql?", method_eq, 1);
    rb_define_method(rb_cUnboundMethod, "hash", method_hash, 0);
    rb_define_method(rb_cUnboundMethod, "clone", method_clone, 0);
    rb_define_method(rb_cUnboundMethod, "arity", method_arity_m, 0);
    rb_define_method(rb_cUnboundMethod, "inspect", method_inspect, 0);
    rb_define_method(rb_cUnboundMethod, "to_s", method_inspect, 0);
    rb_define_method(rb_cUnboundMethod, "name", method_name, 0);
    rb_define_method(rb_cUnboundMethod, "original_name", method_original_name, 0);
    rb_define_method(rb_cUnboundMethod, "owner", method_owner, 0);
    rb_define_method(rb_cUnboundMethod, "bind", umethod_bind, 1);
    rb_define_method(rb_cUnboundMethod, "source_location", rb_method_location, 0);
    rb_define_method(rb_cUnboundMethod, "parameters", rb_method_parameters, 0);
    rb_define_method(rb_cUnboundMethod, "super_method", method_super_method, 0);

    /* Module#*_method */
    rb_define_method(rb_cModule, "instance_method", rb_mod_instance_method, 1);
    rb_define_method(rb_cModule, "public_instance_method", rb_mod_public_instance_method, 1);
    rb_define_private_method(rb_cModule, "define_method", rb_mod_define_method, -1);

    /* Kernel */
    rb_define_method(rb_mKernel, "define_singleton_method", rb_obj_define_method, -1);

    rb_define_private_method(rb_singleton_class(rb_vm_top_self()),
			     "define_method", top_define_method, -1);
}

/*
 *  Objects of class <code>Binding</code> encapsulate the execution
 *  context at some particular place in the code and retain this context
 *  for future use. The variables, methods, value of <code>self</code>,
 *  and possibly an iterator block that can be accessed in this context
 *  are all retained. Binding objects can be created using
 *  <code>Kernel#binding</code>, and are made available to the callback
 *  of <code>Kernel#set_trace_func</code>.
 *
 *  These binding objects can be passed as the second argument of the
 *  <code>Kernel#eval</code> method, establishing an environment for the
 *  evaluation.
 *
 *     class Demo
 *       def initialize(n)
 *         @secret = n
 *       end
 *       def get_binding
 *         return binding()
 *       end
 *     end
 *
 *     k1 = Demo.new(99)
 *     b1 = k1.get_binding
 *     k2 = Demo.new(-3)
 *     b2 = k2.get_binding
 *
 *     eval("@secret", b1)   #=> 99
 *     eval("@secret", b2)   #=> -3
 *     eval("@secret")       #=> nil
 *
 *  Binding objects have no class-specific methods.
 *
 */

void
Init_Binding(void)
{
    rb_cBinding = rb_define_class("Binding", rb_cObject);
    rb_undef_alloc_func(rb_cBinding);
    rb_undef_method(CLASS_OF(rb_cBinding), "new");
    rb_define_method(rb_cBinding, "clone", binding_clone, 0);
    rb_define_method(rb_cBinding, "dup", binding_dup, 0);
    rb_define_method(rb_cBinding, "eval", bind_eval, -1);
    rb_define_method(rb_cBinding, "local_variables", bind_local_variables, 0);
    rb_define_method(rb_cBinding, "local_variable_get", bind_local_variable_get, 1);
    rb_define_method(rb_cBinding, "local_variable_set", bind_local_variable_set, 2);
    rb_define_method(rb_cBinding, "local_variable_defined?", bind_local_variable_defined_p, 1);
    rb_define_method(rb_cBinding, "receiver", bind_receiver, 0);
    rb_define_global_function("binding", rb_f_binding, 0);
}