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POHow to escape Unicode escapes in Groovy's /pattern/ syntax
 

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  1. POHow to escape Unicode escapes in Groovy's /pattern/ syntax
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    <p>The following Groovy commands illustrate my problem.</p> <p>First of all, this works (<a href="http://lotrepls.appspot.com/?language=Groovy&amp;script=%20%22%5Cn%22.matches%28%22%5Cu000A%22%29;?language=Groovy&amp;script=print%20%22a%22.matches%28/%5Cu0061/%29" rel="nofollow noreferrer">as seen on lotrepls.appspot.com</a>) as expected (note that <code>\u0061</code> is <code>'a'</code>).</p> <pre><code>&gt;&gt;&gt; print "a".matches(/\u0061/) true </code></pre> <p>Now let's say that we want to match <code>\n</code>, using the Unicode escape <code>\u000A</code>. The following, using <code>"pattern"</code> as a string, behaves as expected:</p> <pre><code>&gt;&gt;&gt; print "\n".matches("\u000A"); Interpreter exception: com.google.lotrepls.shared.InterpreterException: org.codehaus.groovy.control.MultipleCompilationErrorsException: startup failed, Script1.groovy: 1: expecting anything but ''\n''; got it anyway @ line 1, column 21. 1 error </code></pre> <p>This is expected because in Java at least, Unicode escapes are processed early (<a href="http://java.sun.com/docs/books/jls/third_edition/html/lexical.html#3.3" rel="nofollow noreferrer">JLS 3.3</a>), so:</p> <pre><code>print "\n".matches("\u000A") </code></pre> <p>really is the same as:</p> <pre><code>print "\n".matches(" ") </code></pre> <p>The fix is to escape the Unicode escape, and let the regex engine process it, as follows:</p> <pre><code>&gt;&gt;&gt; print "\n".matches("\\u000A") true </code></pre> <p>Now here's the question part: how can we get this to work with the Groovy <code>/pattern/</code> syntax instead of using string literal?</p> <p>Here are some failed attempts:</p> <pre><code>&gt;&gt;&gt; print "\n".matches(/\u000A/) Interpreter exception: com.google.lotrepls.shared.InterpreterException: org.codehaus.groovy.control.MultipleCompilationErrorsException: startup failed, Script1.groovy: 1: expecting EOF, found '(' @ line 1, column 19. 1 error &gt;&gt;&gt; print "\n".matches(/\\u000A/) false &gt;&gt;&gt; print "\\u000A".matches(/\\u000A/); true </code></pre>
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