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authorErlang/OTP <[email protected]>2009-11-20 14:54:40 +0000
committerErlang/OTP <[email protected]>2009-11-20 14:54:40 +0000
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The R13B03 release.OTP_R13B03
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+<?xml version="1.0" encoding="latin1" ?>
+<!DOCTYPE chapter SYSTEM "chapter.dtd">
+
+<chapter>
+ <header>
+ <copyright>
+ <year>2003</year><year>2009</year>
+ <holder>Ericsson AB. All Rights Reserved.</holder>
+ </copyright>
+ <legalnotice>
+ The contents of this file are subject to the Erlang Public License,
+ Version 1.1, (the "License"); you may not use this file except in
+ compliance with the License. You should have received a copy of the
+ Erlang Public License along with this software. If not, it can be
+ retrieved online at http://www.erlang.org/.
+
+ Software distributed under the License is distributed on an "AS IS"
+ basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
+ the License for the specific language governing rights and limitations
+ under the License.
+
+ </legalnotice>
+
+ <title>Pattern Matching</title>
+ <prepared></prepared>
+ <docno></docno>
+ <date></date>
+ <rev></rev>
+ <file>patterns.xml</file>
+ </header>
+
+ <section>
+ <title>Pattern Matching</title>
+ <p>Variables are bound to values through the <em>pattern matching</em> mechanism. Pattern matching occurs when
+ evaluating a function call, <c>case</c>- <c>receive</c>-
+ <c>try</c>- expressions and match operator (=) expressions.</p>
+ <p>In a pattern matching, a left-hand side
+ <seealso marker="expressions#pattern">pattern</seealso> is matched
+ against a right-hand side
+ <seealso marker="expressions#term">term</seealso>. If
+ the matching succeeds, any unbound variables in the pattern
+ become bound. If the matching fails, a run-time error occurs.</p>
+ <p>Examples:</p>
+ <pre>
+1> <input>X.</input>
+** 1: variable 'X' is unbound **
+2> <input>X = 2.</input>
+2
+3> <input>X + 1.</input>
+3
+4> <input>{X, Y} = {1, 2}.</input>
+** exception error: no match of right hand side value {1,2}
+5> <input>{X, Y} = {2, 3}.</input>
+{2,3}
+6> <input>Y.</input>
+3</pre>
+ </section>
+</chapter>
+