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;;; anaphor.clj -- Anaphoric macros for Clojure
;; by Stuart Sierra <mail@stuartsierra.com>
;; April 7, 2008
;; Copyright (c) 2008 Stuart Sierra. All rights reserved. The use and
;; distribution terms for this software are covered by the Common
;; Public License 1.0 (http://www.opensource.org/licenses/cpl1.0.php)
;; which can be found in the file CPL.TXT at the root of this
;; distribution. By using this software in any fashion, you are
;; agreeing to be bound by the terms of this license. You must not
;; remove this notice, or any other, from this software.
;; This file defines some simple anaphoric macros for Clojure.
;;
;; See "On Lisp" for a description of anaphoric macros:
;; http://www.bookshelf.jp/cgi-bin/goto.cgi?file=onlisp&node=Anaphoric+Macros
;;
;; The macros defined in this file differ slightly from the anaphoric
;; macros in "On Lisp" in that they each take a symbol as their first
;; argument. That symbol is the "anaphor" (for which "On Lisp" always
;; uses "it"). This follows Clojure's preference for non-capturing
;; macros.
(clojure/in-ns 'anaphor)
(clojure/refer 'clojure)
(defmacro aif
"Like 'if', but binds the result of the test to 'symbol' in the
body."
([symbol test then]
`(let [~symbol ~test]
(if ~symbol ~then)))
([symbol test then else]
`(let [~symbol ~test]
(if ~symbol ~then ~else))))
(defmacro awhen
"Like 'when', but binds the result of the test to 'symbol' in the
body."
[symbol test & body]
`(aif ~symbol ~test
(do ~@body)))
(defmacro acond
"Like 'cond', but binds the result of each test to 'symbol' in the
expression body."
[symbol & clauses]
(when clauses
(list 'aif symbol (first clauses)
(second clauses)
(cons 'acond (cons symbol (rest (rest clauses)))))))
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