184 lines
6.4 KiB
HTML
184 lines
6.4 KiB
HTML
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Copyright (C) 1996-1997, 2000-2005, 2009-2023 Free Software Foundation,
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Copyright (C) 2021 Maxime Devos
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Copyright (C) 2024 Tomas Volf
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<title>String Syntax (Guile Reference Manual)</title>
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<link href="Concept-Index.html" rel="index" title="Concept Index">
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<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
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<link href="Strings.html" rel="up" title="Strings">
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<link href="String-Predicates.html" rel="next" title="String Predicates">
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<body lang="en">
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<div class="subsubsection-level-extent" id="String-Syntax">
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<div class="nav-panel">
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<p>
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Next: <a href="String-Predicates.html" accesskey="n" rel="next">String Predicates</a>, Up: <a href="Strings.html" accesskey="u" rel="up">Strings</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html" title="Index" rel="index">Index</a>]</p>
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</div>
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<hr>
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<h4 class="subsubsection" id="String-Read-Syntax"><span>6.6.5.1 String Read Syntax<a class="copiable-link" href="#String-Read-Syntax"> ¶</a></span></h4>
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<p>The read syntax for strings is an arbitrarily long sequence of
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characters enclosed in double quotes (<code class="code">"</code>).
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</p>
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<p>Backslash is an escape character and can be used to insert the following
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special characters. <code class="code">\"</code> and <code class="code">\\</code> are R5RS standard,
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<code class="code">\|</code> is R7RS standard, the next seven are R6RS standard —
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notice they follow C syntax — and the remaining four are Guile
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extensions.
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</p>
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<dl class="table">
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<dt><code class="code">\\</code></dt>
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<dd><p>Backslash character.
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</p>
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</dd>
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<dt><code class="code">\"</code></dt>
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<dd><p>Double quote character (an unescaped <code class="code">"</code> is otherwise the end
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of the string).
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</p>
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</dd>
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<dt><code class="code">\|</code></dt>
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<dd><p>Vertical bar character.
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</p>
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</dd>
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<dt><code class="code">\a</code></dt>
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<dd><p>Bell character (ASCII 7).
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</p>
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</dd>
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<dt><code class="code">\f</code></dt>
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<dd><p>Formfeed character (ASCII 12).
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</p>
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</dd>
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<dt><code class="code">\n</code></dt>
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<dd><p>Newline character (ASCII 10).
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</p>
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</dd>
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<dt><code class="code">\r</code></dt>
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<dd><p>Carriage return character (ASCII 13).
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</p>
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</dd>
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<dt><code class="code">\t</code></dt>
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<dd><p>Tab character (ASCII 9).
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</p>
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</dd>
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<dt><code class="code">\v</code></dt>
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<dd><p>Vertical tab character (ASCII 11).
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</p>
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</dd>
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<dt><code class="code">\b</code></dt>
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<dd><p>Backspace character (ASCII 8).
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</p>
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</dd>
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<dt><code class="code">\0</code></dt>
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<dd><p>NUL character (ASCII 0).
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</p>
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</dd>
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<dt><code class="code">\(</code></dt>
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<dd><p>Open parenthesis. This is intended for use at the beginning of lines in
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multiline strings to avoid confusing Emacs lisp modes.
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</p>
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</dd>
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<dt><code class="code">\</code> followed by newline (ASCII 10)</dt>
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<dd><p>Nothing. This way if <code class="code">\</code> is the last character in a line, the
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string will continue with the first character from the next line,
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without a line break.
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</p>
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<p>If the <code class="code">hungry-eol-escapes</code> reader option is enabled, which is not
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the case by default, leading whitespace on the next line is discarded.
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</p>
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<div class="example lisp">
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<pre class="lisp-preformatted">"foo\
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bar"
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⇒ "foo bar"
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(read-enable 'hungry-eol-escapes)
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"foo\
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bar"
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⇒ "foobar"
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</pre></div>
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</dd>
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<dt><code class="code">\xHH</code></dt>
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<dd><p>Character code given by two hexadecimal digits. For example
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<code class="code">\x7f</code> for an ASCII DEL (127).
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</p>
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</dd>
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<dt><code class="code">\uHHHH</code></dt>
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<dd><p>Character code given by four hexadecimal digits. For example
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<code class="code">\u0100</code> for a capital A with macron (U+0100).
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</p>
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</dd>
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<dt><code class="code">\UHHHHHH</code></dt>
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<dd><p>Character code given by six hexadecimal digits. For example
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<code class="code">\U010402</code>.
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</p></dd>
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</dl>
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<p>The following are examples of string literals:
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</p>
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<div class="example lisp">
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<pre class="lisp-preformatted">"foo"
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"bar plonk"
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"Hello World"
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"\"Hi\", he said."
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</pre></div>
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<p>The three escape sequences <code class="code">\xHH</code>, <code class="code">\uHHHH</code> and <code class="code">\UHHHHHH</code> were
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chosen to not break compatibility with code written for previous versions of
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Guile. The R6RS specification suggests a different, incompatible syntax for hex
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escapes: <code class="code">\xHHHH;</code> – a character code followed by one to eight hexadecimal
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digits terminated with a semicolon. If this escape format is desired instead,
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it can be enabled with the reader option <code class="code">r6rs-hex-escapes</code>.
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</p>
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<div class="example lisp">
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<pre class="lisp-preformatted">(read-enable 'r6rs-hex-escapes)
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</pre></div>
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<p>For more on reader options, See <a class="xref" href="Scheme-Read.html">Reading Scheme Code</a>.
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</p>
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</div>
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<hr>
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<div class="nav-panel">
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<p>
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Next: <a href="String-Predicates.html">String Predicates</a>, Up: <a href="Strings.html">Strings</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html" title="Index" rel="index">Index</a>]</p>
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</div>
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</body>
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