diff options
Diffstat (limited to 'modules/fcase')
| -rw-r--r-- | modules/fcase/pom.xml | 16 | ||||
| -rw-r--r-- | modules/fcase/src/main/clojure/clojure/contrib/fcase.clj | 108 |
2 files changed, 124 insertions, 0 deletions
diff --git a/modules/fcase/pom.xml b/modules/fcase/pom.xml new file mode 100644 index 00000000..1fb6f9a8 --- /dev/null +++ b/modules/fcase/pom.xml @@ -0,0 +1,16 @@ +<?xml version="1.0" encoding="UTF-8"?> +<project xmlns="http://maven.apache.org/POM/4.0.0" + xmlns:xsi="http//www.w3.org/2001/XMLSchema-instance" + xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 + http://maven.apache.org/maven-v4_0_0.xsd"> + <modelVersion>4.0.0</modelVersion> + <parent> + <groupId>org.clojure.contrib</groupId> + <artifactId>parent</artifactId> + <version>1.3.0-SNAPSHOT</version> + <relativePath>../parent</relativePath> + </parent> + <artifactId>fcase</artifactId> + <dependencies> + </dependencies> +</project>
\ No newline at end of file diff --git a/modules/fcase/src/main/clojure/clojure/contrib/fcase.clj b/modules/fcase/src/main/clojure/clojure/contrib/fcase.clj new file mode 100644 index 00000000..4d0fc184 --- /dev/null +++ b/modules/fcase/src/main/clojure/clojure/contrib/fcase.clj @@ -0,0 +1,108 @@ +;;; fcase.clj -- simple variants of "case" for Clojure + +;; by Stuart Sierra, http://stuartsierra.com/ +;; April 7, 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. + + +;; This file defines a generic "case" macro called "fcase" which takes +;; the equality-testing function as an argument. It also defines a +;; traditional "case" macro that tests using "=" and variants that +;; test for regular expressions and class membership. + + +;; Note (December 23, 2008): This library has been supplanted by the +;; inclusion of "condp" in clojure.core as of Clojure SVN rev. 1180. + + +(ns + ^{:author "Stuart Sierra", + :doc "This file defines a generic \"case\" macro called \"fcase\" which takes +the equality-testing function as an argument. It also defines a +traditional \"case\" macro that tests using \"=\" and variants that +test for regular expressions and class membership. + + +Note (December 23, 2008): This library has been supplanted by the +inclusion of \"condp\" in clojure.core as of Clojure SVN rev. 1180."} + + clojure.contrib.fcase + (:refer-clojure :exclude (case))) + + +(defmacro fcase + "Generic switch/case macro. 'fcase' is short for 'function case'. + + The 'compare-fn' is a fn of two arguments. + + The 'test-expr-clauses' are value-expression pairs without + surrounding parentheses, like in Clojure's 'cond'. + + The 'case-value' is evaluated once and cached. Then, 'compare-fn' + is called once for each clause, with the clause's test value as its + first argument and 'case-value' as its second argument. If + 'compare-fn' returns logical true, the clause's expression is + evaluated and returned. If 'compare-fn' returns false/nil, we go to + the next test value. + + If 'test-expr-clauses' contains an odd number of items, the last + item is the default expression evaluated if no case-value matches. + If there is no default expression and no case-value matches, fcase + returns nil. + + See specific forms of this macro in 'case' and 're-case'. + + The test expressions in 'fcase' are always evaluated linearly, in + order. For a large number of case expressions it may be more + efficient to use a hash lookup." + [compare-fn case-value & + test-expr-clauses] + (let [test-val-sym (gensym "test_val") + test-fn-sym (gensym "test_fn") + cond-loop (fn this [clauses] + (cond + (>= (count clauses) 2) + (list 'if (list test-fn-sym (first clauses) test-val-sym) + (second clauses) + (this (rest (rest clauses)))) + (= (count clauses) 1) (first clauses)))] + (list 'let [test-val-sym case-value, test-fn-sym compare-fn] + (cond-loop test-expr-clauses)))) + +(defmacro case + "Like cond, but test-value is compared against the value of each + test expression with =. If they are equal, executes the \"body\" + expression. Optional last expression is executed if none of the + test expressions match." + [test-value & clauses] + `(fcase = ~test-value ~@clauses)) + +(defmacro re-case + "Like case, but the test expressions are regular expressions, tested + with re-find." + [test-value & clauses] + `(fcase re-find ~test-value ~@clauses)) + +(defmacro instance-case + "Like case, but the test expressions are Java class names, tested with + 'instance?'." + [test-value & clauses] + `(fcase instance? ~test-value ~@clauses)) + +(defn in-case-test [test-seq case-value] + (some (fn [item] (= item case-value)) + test-seq)) + +(defmacro in-case + "Like case, but test expressions are sequences. The test expression + is true if any item in the sequence is equal (tested with '=') to + the test value." + [test-value & clauses] + `(fcase in-case-test ~test-value ~@clauses)) |