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+;;; condp.clj - generic case-like macro using template expressions
+
+;; By Stuart Sierra, http://stuartsierra.com/
+;; December 15, 2008
+
+;; Copyright (c) Stuart Sierra, 2008. 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.
+
+
+(ns clojure.contrib.condp
+    (:require clojure.contrib.template))
+
+(defmacro condp
+  "expr is a template expression (see template), clauses are test/expr
+  pairs like cond.  Evalautes the template on each test value, one at
+  a time.  If a test returns logical true, condp evaluates the
+  corresponding expr and returns its value.  If none of the tests are
+  true, and there are an odd number of clauses, the last clause is
+  evaluated, otherwise returns nil."
+  [expr & clauses]
+  (let [test-fn-sym (gensym "test_")
+        f (fn this [c]
+            (cond
+             (empty? c) nil
+             (= 1 (count c)) (first c)
+             :else (list 'if (list test-fn-sym (first c))
+                         (second c)
+                         (this (rrest c)))))]
+    `(let [~test-fn-sym (clojure.contrib.template/template ~expr)]
+       ~(f clauses))))
+
+(defmacro econdp
+  "Like condp but throws Exception if no tests match."
+  [expr & clauses]
+  (let [test-fn-sym (gensym "test_")
+        f (fn this [c]
+              (cond
+               (empty? c) '(throw (Exception. "Nothing matched in econdp."))
+               (= 1 (count c)) (throw (IllegalStateException. "Odd number of clauses in econdp."))
+               :else (list 'if (list test-fn-sym (first c))
+                           (second c)
+                           (this (rrest c)))))]
+    `(let [~test-fn-sym (clojure.contrib.template/template ~expr)]
+       ~(f clauses))))