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;;; subr-x.el --- extra Lisp functions -*- lexical-binding:t -*-
;; Copyright (C) 2013-2015 Free Software Foundation, Inc.
;; Maintainer: emacs-devel@gnu.org
;; Keywords: convenience
;; Package: emacs
;; This file is part of GNU Emacs.
;; GNU Emacs is free software: you can redistribute it and/or modify
;; it under the terms of the GNU General Public License as published by
;; the Free Software Foundation, either version 3 of the License, or
;; (at your option) any later version.
;; GNU Emacs is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
;; GNU General Public License for more details.
;; You should have received a copy of the GNU General Public License
;; along with GNU Emacs. If not, see <http://www.gnu.org/licenses/>.
;;; Commentary:
;; Less commonly used functions that complement basic APIs, often implemented in
;; C code (like hash-tables and strings), and are not eligible for inclusion
;; in subr.el.
;; Do not document these functions in the lispref.
;; http://lists.gnu.org/archive/html/emacs-devel/2014-01/msg01006.html
;;; Code:
(require 'pcase)
(defmacro internal--thread-argument (first? &rest forms)
"Internal implementation for `thread-first' and `thread-last'.
When Argument FIRST? is non-nil argument is threaded first, else
last. FORMS are the expressions to be threaded."
(pcase forms
(`(,x (,f . ,args) . ,rest)
`(internal--thread-argument
,first? ,(if first? `(,f ,x ,@args) `(,f ,@args ,x)) ,@rest))
(`(,x ,f . ,rest) `(internal--thread-argument ,first? (,f ,x) ,@rest))
(_ (car forms))))
(defmacro thread-first (&rest forms)
"Thread FORMS elements as the first argument of their successor.
Example:
(thread-first
5
(+ 20)
(/ 25)
-
(+ 40))
Is equivalent to:
(+ (- (/ (+ 5 20) 25)) 40)
Note how the single `-' got converted into a list before
threading."
(declare (indent 1)
(debug (form &rest [&or symbolp (sexp &rest form)])))
`(internal--thread-argument t ,@forms))
(defmacro thread-last (&rest forms)
"Thread FORMS elements as the last argument of their successor.
Example:
(thread-last
5
(+ 20)
(/ 25)
-
(+ 40))
Is equivalent to:
(+ 40 (- (/ 25 (+ 20 5))))
Note how the single `-' got converted into a list before
threading."
(declare (indent 1) (debug thread-first))
`(internal--thread-argument nil ,@forms))
(defsubst internal--listify (elt)
"Wrap ELT in a list if it is not one."
(if (not (listp elt))
(list elt)
elt))
(defsubst internal--check-binding (binding)
"Check BINDING is properly formed."
(when (> (length binding) 2)
(signal
'error
(cons "`let' bindings can have only one value-form" binding)))
binding)
(defsubst internal--build-binding-value-form (binding prev-var)
"Build the conditional value form for BINDING using PREV-VAR."
`(,(car binding) (and ,prev-var ,(cadr binding))))
(defun internal--build-binding (binding prev-var)
"Check and build a single BINDING with PREV-VAR."
(thread-first
binding
internal--listify
internal--check-binding
(internal--build-binding-value-form prev-var)))
(defun internal--build-bindings (bindings)
"Check and build conditional value forms for BINDINGS."
(let ((prev-var t))
(mapcar (lambda (binding)
(let ((binding (internal--build-binding binding prev-var)))
(setq prev-var (car binding))
binding))
bindings)))
(defmacro if-let (bindings then &rest else)
"Process BINDINGS and if all values are non-nil eval THEN, else ELSE.
Argument BINDINGS is a list of tuples whose car is a symbol to be
bound and (optionally) used in THEN, and its cadr is a sexp to be
evalled to set symbol's value. In the special case you only want
to bind a single value, BINDINGS can just be a plain tuple."
(declare (indent 2)
(debug ([&or (&rest (symbolp form)) (symbolp form)] form body)))
(when (and (<= (length bindings) 2)
(not (listp (car bindings))))
;; Adjust the single binding case
(setq bindings (list bindings)))
`(let* ,(internal--build-bindings bindings)
(if ,(car (internal--listify (car (last bindings))))
,then
,@else)))
(defmacro when-let (bindings &rest body)
"Process BINDINGS and if all values are non-nil eval BODY.
Argument BINDINGS is a list of tuples whose car is a symbol to be
bound and (optionally) used in BODY, and its cadr is a sexp to be
evalled to set symbol's value. In the special case you only want
to bind a single value, BINDINGS can just be a plain tuple."
(declare (indent 1) (debug if-let))
(list 'if-let bindings (macroexp-progn body)))
(defsubst hash-table-empty-p (hash-table)
"Check whether HASH-TABLE is empty (has 0 elements)."
(zerop (hash-table-count hash-table)))
(defsubst hash-table-keys (hash-table)
"Return a list of keys in HASH-TABLE."
(let ((keys '()))
(maphash (lambda (k _v) (push k keys)) hash-table)
keys))
(defsubst hash-table-values (hash-table)
"Return a list of values in HASH-TABLE."
(let ((values '()))
(maphash (lambda (_k v) (push v values)) hash-table)
values))
(defsubst string-empty-p (string)
"Check whether STRING is empty."
(string= string ""))
(defsubst string-join (strings &optional separator)
"Join all STRINGS using SEPARATOR."
(mapconcat 'identity strings separator))
(define-obsolete-function-alias 'string-reverse 'reverse "25.1")
(defsubst string-trim-left (string)
"Remove leading whitespace from STRING."
(if (string-match "\\`[ \t\n\r]+" string)
(replace-match "" t t string)
string))
(defsubst string-trim-right (string)
"Remove trailing whitespace from STRING."
(if (string-match "[ \t\n\r]+\\'" string)
(replace-match "" t t string)
string))
(defsubst string-trim (string)
"Remove leading and trailing whitespace from STRING."
(string-trim-left (string-trim-right string)))
(defsubst string-blank-p (string)
"Check whether STRING is either empty or only whitespace."
(string-match-p "\\`[ \t\n\r]*\\'" string))
(defsubst string-remove-prefix (prefix string)
"Remove PREFIX from STRING if present."
(if (string-prefix-p prefix string)
(substring string (length prefix))
string))
(defsubst string-remove-suffix (suffix string)
"Remove SUFFIX from STRING if present."
(if (string-suffix-p suffix string)
(substring string 0 (- (length string) (length suffix)))
string))
(provide 'subr-x)
;;; subr-x.el ends here
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