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;;; template.clj - anonymous functions that pre-evaluate sub-expressions
;; By Stuart Sierra, http://stuartsierra.com/
;; June 23, 2009
;; Copyright (c) Stuart Sierra, 2009. All rights reserved. The use
;; and distribution terms for this software are covered by the Eclipse
;; Public License 1.0 (http://opensource.org/licenses/eclipse-1.0.php)
;; which can be found in the file epl-v10.html 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.
;; CHANGE LOG
;;
;; June 23, 2009: complete rewrite, eliminated _1,_2,... argument
;; syntax
;;
;; January 20, 2009: added "template?" and checks for valid template
;; expressions.
;;
;; December 15, 2008: first version
(ns #^{:author "Stuart Sierra"
:doc "Macros that expand to repeated copies of a template expression."}
clojure.contrib.template
(:require [clojure.contrib.walk :as walk]))
(defn apply-template
"For use in macros. argv is an argument list, as in defn. expr is
a quoted expression using the symbols in argv. values is a sequence
of values to be used for the arguments.
apply-template will recursively replace argument symbols in expr
with their corresponding values, returning a modified expr.
Example: (apply-template '[x] '(+ x x) '[2])
;=> (+ 2 2)"
[argv expr values]
(assert (vector? argv))
(assert (every? symbol? argv))
(walk/prewalk-replace (zipmap argv values) expr))
(defmacro do-template
"Repeatedly copies expr (in a do block) for each group of arguments
in values. values are automatically partitioned by the number of
arguments in argv, an argument vector as in defn.
Example: (macroexpand '(do-template [x y] (+ y x) 2 4 3 5))
;=> (do (+ 4 2) (+ 5 3))"
[argv expr & values]
(let [c (count argv)]
`(do ~@(map (fn [a] (apply-template argv expr a))
(partition c values)))))
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