diff options
Diffstat (limited to 'example/closurecalc/calc.py')
| -rw-r--r-- | example/closurecalc/calc.py | 44 |
1 files changed, 23 insertions, 21 deletions
diff --git a/example/closurecalc/calc.py b/example/closurecalc/calc.py index 6598f58..6031b05 100644 --- a/example/closurecalc/calc.py +++ b/example/closurecalc/calc.py @@ -2,37 +2,38 @@ # calc.py # # A calculator parser that makes use of closures. The function make_calculator() -# returns a function that accepts an input string and returns a result. All +# returns a function that accepts an input string and returns a result. All # lexing rules, parsing rules, and internal state are held inside the function. # ----------------------------------------------------------------------------- import sys -sys.path.insert(0,"../..") +sys.path.insert(0, "../..") if sys.version_info[0] >= 3: raw_input = input # Make a calculator function + def make_calculator(): import ply.lex as lex import ply.yacc as yacc # ------- Internal calculator state - variables = { } # Dictionary of stored variables + variables = {} # Dictionary of stored variables # ------- Calculator tokenizing rules tokens = ( - 'NAME','NUMBER', + 'NAME', 'NUMBER', ) - literals = ['=','+','-','*','/', '(',')'] + literals = ['=', '+', '-', '*', '/', '(', ')'] t_ignore = " \t" - t_NAME = r'[a-zA-Z_][a-zA-Z0-9_]*' + t_NAME = r'[a-zA-Z_][a-zA-Z0-9_]*' def t_NUMBER(t): r'\d+' @@ -42,20 +43,20 @@ def make_calculator(): def t_newline(t): r'\n+' t.lexer.lineno += t.value.count("\n") - + def t_error(t): print("Illegal character '%s'" % t.value[0]) t.lexer.skip(1) - + # Build the lexer lexer = lex.lex() # ------- Calculator parsing rules precedence = ( - ('left','+','-'), - ('left','*','/'), - ('right','UMINUS'), + ('left', '+', '-'), + ('left', '*', '/'), + ('right', 'UMINUS'), ) def p_statement_assign(p): @@ -72,10 +73,14 @@ def make_calculator(): | expression '-' expression | expression '*' expression | expression '/' expression''' - if p[2] == '+' : p[0] = p[1] + p[3] - elif p[2] == '-': p[0] = p[1] - p[3] - elif p[2] == '*': p[0] = p[1] * p[3] - elif p[2] == '/': p[0] = p[1] / p[3] + if p[2] == '+': + p[0] = p[1] + p[3] + elif p[2] == '-': + p[0] = p[1] - p[3] + elif p[2] == '*': + p[0] = p[1] * p[3] + elif p[2] == '/': + p[0] = p[1] / p[3] def p_expression_uminus(p): "expression : '-' expression %prec UMINUS" @@ -103,14 +108,13 @@ def make_calculator(): else: print("Syntax error at EOF") - # Build the parser parser = yacc.yacc() - # ------- Input function - + # ------- Input function + def input(text): - result = parser.parse(text,lexer=lexer) + result = parser.parse(text, lexer=lexer) return result return input @@ -126,5 +130,3 @@ while True: r = calc(s) if r: print(r) - - |