154 lines
5.4 KiB
HTML
154 lines
5.4 KiB
HTML
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<!DOCTYPE html>
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<html>
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<!-- Created by GNU Texinfo 7.1, https://www.gnu.org/software/texinfo/ -->
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
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<!-- This manual documents Guile version 3.0.10.
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Copyright (C) 1996-1997, 2000-2005, 2009-2023 Free Software Foundation,
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Inc.
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Copyright (C) 2021 Maxime Devos
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Copyright (C) 2024 Tomas Volf
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Permission is granted to copy, distribute and/or modify this document
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under the terms of the GNU Free Documentation License, Version 1.3 or
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any later version published by the Free Software Foundation; with no
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Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A
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copy of the license is included in the section entitled "GNU Free
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Documentation License." -->
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<title>Number Syntax (Guile Reference Manual)</title>
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<meta name="description" content="Number Syntax (Guile Reference Manual)">
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<meta name="keywords" content="Number Syntax (Guile Reference Manual)">
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<meta name="resource-type" content="document">
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<meta name="distribution" content="global">
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<meta name="Generator" content=".texi2any-real">
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<meta name="viewport" content="width=device-width,initial-scale=1">
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<link href="index.html" rel="start" title="Top">
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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="Numbers.html" rel="up" title="Numbers">
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<link href="Integer-Operations.html" rel="next" title="Integer Operations">
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<link href="Exactness.html" rel="prev" title="Exactness">
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<style type="text/css">
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a.copiable-link {visibility: hidden; text-decoration: none; line-height: 0em}
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span:hover a.copiable-link {visibility: visible}
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</style>
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<link rel="stylesheet" type="text/css" href="https://www.gnu.org/software/gnulib/manual.css">
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</head>
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<body lang="en">
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<div class="subsubsection-level-extent" id="Number-Syntax">
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<div class="nav-panel">
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<p>
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Next: <a href="Integer-Operations.html" accesskey="n" rel="next">Operations on Integer Values</a>, Previous: <a href="Exactness.html" accesskey="p" rel="prev">Exact and Inexact Numbers</a>, Up: <a href="Numbers.html" accesskey="u" rel="up">Numerical data types</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="Read-Syntax-for-Numerical-Data"><span>6.6.2.6 Read Syntax for Numerical Data<a class="copiable-link" href="#Read-Syntax-for-Numerical-Data"> ¶</a></span></h4>
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<p>The read syntax for integers is a string of digits, optionally
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preceded by a minus or plus character, a code indicating the
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base in which the integer is encoded, and a code indicating whether
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the number is exact or inexact. The supported base codes are:
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</p>
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<dl class="table">
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<dt><code class="code">#b</code></dt>
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<dt><code class="code">#B</code></dt>
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<dd><p>the integer is written in binary (base 2)
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</p>
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</dd>
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<dt><code class="code">#o</code></dt>
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<dt><code class="code">#O</code></dt>
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<dd><p>the integer is written in octal (base 8)
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</p>
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</dd>
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<dt><code class="code">#d</code></dt>
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<dt><code class="code">#D</code></dt>
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<dd><p>the integer is written in decimal (base 10)
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</p>
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</dd>
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<dt><code class="code">#x</code></dt>
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<dt><code class="code">#X</code></dt>
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<dd><p>the integer is written in hexadecimal (base 16)
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</p></dd>
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</dl>
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<p>If the base code is omitted, the integer is assumed to be decimal. The
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following examples show how these base codes are used.
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</p>
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<div class="example lisp">
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<pre class="lisp-preformatted">-13
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⇒ -13
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#d-13
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⇒ -13
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#x-13
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⇒ -19
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#b+1101
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⇒ 13
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#o377
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⇒ 255
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</pre></div>
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<p>The codes for indicating exactness (which can, incidentally, be applied
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to all numerical values) are:
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</p>
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<dl class="table">
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<dt><code class="code">#e</code></dt>
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<dt><code class="code">#E</code></dt>
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<dd><p>the number is exact
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</p>
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</dd>
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<dt><code class="code">#i</code></dt>
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<dt><code class="code">#I</code></dt>
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<dd><p>the number is inexact.
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</p></dd>
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</dl>
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<p>If the exactness indicator is omitted, the number is exact unless it
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contains a radix point. Since Guile can not represent exact complex
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numbers, an error is signaled when asking for them.
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</p>
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<div class="example lisp">
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<pre class="lisp-preformatted">(exact? 1.2)
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⇒ #f
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(exact? #e1.2)
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⇒ #t
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(exact? #e+1i)
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ERROR: Wrong type argument
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</pre></div>
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<p>Guile also understands the syntax ‘<samp class="samp">+inf.0</samp>’ and ‘<samp class="samp">-inf.0</samp>’ for
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plus and minus infinity, respectively. The value must be written
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exactly as shown, that is, they always must have a sign and exactly
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one zero digit after the decimal point. It also understands
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‘<samp class="samp">+nan.0</samp>’ and ‘<samp class="samp">-nan.0</samp>’ for the special ‘not-a-number’ value.
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The sign is ignored for ‘not-a-number’ and the value is always printed
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as ‘<samp class="samp">+nan.0</samp>’.
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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="Integer-Operations.html">Operations on Integer Values</a>, Previous: <a href="Exactness.html">Exact and Inexact Numbers</a>, Up: <a href="Numbers.html">Numerical data types</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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</html>
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