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144 lines
7.7 KiB
HTML
144 lines
7.7 KiB
HTML
4 years ago
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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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<html>
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<!-- This manual describes how to install and use the GNU multiple precision
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arithmetic library, version 6.1.0.
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Copyright 1991, 1993-2015 Free Software Foundation, Inc.
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Permission is granted to copy, distribute and/or modify this document under
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the terms of the GNU Free Documentation License, Version 1.3 or any later
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version published by the Free Software Foundation; with no Invariant Sections,
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with the Front-Cover Texts being "A GNU Manual", and with the Back-Cover
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Texts being "You have freedom to copy and modify this GNU Manual, like GNU
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software". A copy of the license is included in
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GNU Free Documentation License. -->
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<!-- Created by GNU Texinfo 6.4, http://www.gnu.org/software/texinfo/ -->
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<head>
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<title>Formatted Input Functions (GNU MP 6.1.0)</title>
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<meta name="description" content="How to install and use the GNU multiple precision arithmetic library, version 6.1.0.">
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<meta name="keywords" content="Formatted Input Functions (GNU MP 6.1.0)">
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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="makeinfo">
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<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
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<link href="index.html#Top" rel="start" title="Top">
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<link href="Concept-Index.html#Concept-Index" rel="index" title="Concept Index">
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<link href="Formatted-Input.html#Formatted-Input" rel="up" title="Formatted Input">
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<link href="C_002b_002b-Formatted-Input.html#C_002b_002b-Formatted-Input" rel="next" title="C++ Formatted Input">
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<link href="Formatted-Input-Strings.html#Formatted-Input-Strings" rel="prev" title="Formatted Input Strings">
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-->
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</style>
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</head>
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<body lang="en">
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<a name="Formatted-Input-Functions"></a>
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<div class="header">
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<p>
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Next: <a href="C_002b_002b-Formatted-Input.html#C_002b_002b-Formatted-Input" accesskey="n" rel="next">C++ Formatted Input</a>, Previous: <a href="Formatted-Input-Strings.html#Formatted-Input-Strings" accesskey="p" rel="prev">Formatted Input Strings</a>, Up: <a href="Formatted-Input.html#Formatted-Input" accesskey="u" rel="up">Formatted Input</a> [<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p>
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</div>
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<hr>
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<a name="Formatted-Input-Functions-1"></a>
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<h3 class="section">11.2 Formatted Input Functions</h3>
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<a name="index-Input-functions-3"></a>
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<p>Each of the following functions is similar to the corresponding C library
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function. The plain <code>scanf</code> forms take a variable argument list. The
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<code>vscanf</code> forms take an argument pointer, see <a href="http://www.gnu.org/software/libc/manual/html_node/Variadic-Functions.html#Variadic-Functions">Variadic Functions</a> in <cite>The GNU C Library Reference Manual</cite>, or ‘<samp>man 3
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va_start</samp>’.
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</p>
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<p>It should be emphasised that if a format string is invalid, or the arguments
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don’t match what the format specifies, then the behaviour of any of these
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functions will be unpredictable. GCC format string checking is not available,
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since it doesn’t recognise the GMP extensions.
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</p>
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<p>No overlap is permitted between the <var>fmt</var> string and any of the results
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produced.
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</p>
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<dl>
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<dt><a name="index-gmp_005fscanf"></a>Function: <em>int</em> <strong>gmp_scanf</strong> <em>(const char *<var>fmt</var>, …)</em></dt>
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<dt><a name="index-gmp_005fvscanf"></a>Function: <em>int</em> <strong>gmp_vscanf</strong> <em>(const char *<var>fmt</var>, va_list <var>ap</var>)</em></dt>
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<dd><p>Read from the standard input <code>stdin</code>.
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</p></dd></dl>
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<dl>
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<dt><a name="index-gmp_005ffscanf"></a>Function: <em>int</em> <strong>gmp_fscanf</strong> <em>(FILE *<var>fp</var>, const char *<var>fmt</var>, …)</em></dt>
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<dt><a name="index-gmp_005fvfscanf"></a>Function: <em>int</em> <strong>gmp_vfscanf</strong> <em>(FILE *<var>fp</var>, const char *<var>fmt</var>, va_list <var>ap</var>)</em></dt>
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<dd><p>Read from the stream <var>fp</var>.
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</p></dd></dl>
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<dl>
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<dt><a name="index-gmp_005fsscanf"></a>Function: <em>int</em> <strong>gmp_sscanf</strong> <em>(const char *<var>s</var>, const char *<var>fmt</var>, …)</em></dt>
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<dt><a name="index-gmp_005fvsscanf"></a>Function: <em>int</em> <strong>gmp_vsscanf</strong> <em>(const char *<var>s</var>, const char *<var>fmt</var>, va_list <var>ap</var>)</em></dt>
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<dd><p>Read from a null-terminated string <var>s</var>.
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</p></dd></dl>
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<p>The return value from each of these functions is the same as the standard C99
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<code>scanf</code>, namely the number of fields successfully parsed and stored.
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‘<samp>%n</samp>’ fields and fields read but suppressed by ‘<samp>*</samp>’ don’t count
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towards the return value.
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</p>
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<p>If end of input (or a file error) is reached before a character for a field or
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a literal, and if no previous non-suppressed fields have matched, then the
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return value is <code>EOF</code> instead of 0. A whitespace character in the format
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string is only an optional match and doesn’t induce an <code>EOF</code> in this
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fashion. Leading whitespace read and discarded for a field don’t count as
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characters for that field.
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</p>
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<p>For the GMP types, input parsing follows C99 rules, namely one character of
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lookahead is used and characters are read while they continue to meet the
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format requirements. If this doesn’t provide a complete number then the
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function terminates, with that field not stored nor counted towards the return
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value. For instance with <code>mpf_t</code> an input ‘<samp>1.23e-XYZ</samp>’ would be read
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up to the ‘<samp>X</samp>’ and that character pushed back since it’s not a digit. The
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string ‘<samp>1.23e-</samp>’ would then be considered invalid since an ‘<samp>e</samp>’ must
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be followed by at least one digit.
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</p>
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<p>For the standard C types, in the current implementation GMP calls the C
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library <code>scanf</code> functions, which might have looser rules about what
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constitutes a valid input.
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</p>
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<p>Note that <code>gmp_sscanf</code> is the same as <code>gmp_fscanf</code> and only does one
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character of lookahead when parsing. Although clearly it could look at its
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entire input, it is deliberately made identical to <code>gmp_fscanf</code>, the same
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way C99 <code>sscanf</code> is the same as <code>fscanf</code>.
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</p>
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<hr>
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<div class="header">
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<p>
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Next: <a href="C_002b_002b-Formatted-Input.html#C_002b_002b-Formatted-Input" accesskey="n" rel="next">C++ Formatted Input</a>, Previous: <a href="Formatted-Input-Strings.html#Formatted-Input-Strings" accesskey="p" rel="prev">Formatted Input Strings</a>, Up: <a href="Formatted-Input.html#Formatted-Input" accesskey="u" rel="up">Formatted Input</a> [<a href="Concept-Index.html#Concept-Index" 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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