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diff --git a/share/doc/gfortran/Hollerith-constants-support.html b/share/doc/gfortran/Hollerith-constants-support.html new file mode 100644 index 0000000..68cdf1d --- /dev/null +++ b/share/doc/gfortran/Hollerith-constants-support.html @@ -0,0 +1,142 @@ +<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> +<html> +<!-- Copyright (C) 1999-2023 Free Software Foundation, Inc. + +Permission is granted to copy, distribute and/or modify this document +under the terms of the GNU Free Documentation License, Version 1.3 or +any later version published by the Free Software Foundation; with the +Invariant Sections being "Funding Free Software", the Front-Cover +Texts being (a) (see below), and with the Back-Cover Texts being (b) +(see below). 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Copies published by the Free Software Foundation raise + funds for GNU development. --> +<!-- Created by GNU Texinfo 5.1, http://www.gnu.org/software/texinfo/ --> +<head> +<title>The GNU Fortran Compiler: Hollerith constants support</title> + +<meta name="description" content="The GNU Fortran Compiler: Hollerith constants support"> +<meta name="keywords" content="The GNU Fortran Compiler: Hollerith constants support"> +<meta name="resource-type" content="document"> +<meta name="distribution" content="global"> +<meta name="Generator" content="makeinfo"> +<meta http-equiv="Content-Type" content="text/html; charset=utf-8"> +<link href="index.html#Top" rel="start" title="Top"> +<link href="Option-Index.html#Option-Index" rel="index" title="Option Index"> +<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents"> +<link href="Extensions-implemented-in-GNU-Fortran.html#Extensions-implemented-in-GNU-Fortran" rel="up" title="Extensions implemented in GNU Fortran"> +<link href="Character-conversion.html#Character-conversion" rel="next" title="Character conversion"> +<link href="Implicitly-convert-LOGICAL-and-INTEGER-values.html#Implicitly-convert-LOGICAL-and-INTEGER-values" rel="previous" title="Implicitly convert LOGICAL and INTEGER values"> +<style type="text/css"> +<!-- +a.summary-letter {text-decoration: none} +blockquote.smallquotation {font-size: smaller} +div.display {margin-left: 3.2em} +div.example {margin-left: 3.2em} +div.indentedblock {margin-left: 3.2em} +div.lisp {margin-left: 3.2em} +div.smalldisplay {margin-left: 3.2em} +div.smallexample {margin-left: 3.2em} +div.smallindentedblock {margin-left: 3.2em; font-size: smaller} +div.smalllisp {margin-left: 3.2em} +kbd {font-style:oblique} +pre.display {font-family: inherit} +pre.format {font-family: inherit} +pre.menu-comment {font-family: serif} +pre.menu-preformatted {font-family: serif} +pre.smalldisplay {font-family: inherit; font-size: smaller} +pre.smallexample {font-size: smaller} +pre.smallformat {font-family: inherit; font-size: smaller} +pre.smalllisp {font-size: smaller} +span.nocodebreak {white-space:nowrap} +span.nolinebreak {white-space:nowrap} +span.roman {font-family:serif; font-weight:normal} +span.sansserif {font-family:sans-serif; font-weight:normal} +ul.no-bullet {list-style: none} +--> +</style> + + +</head> + +<body lang="en" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000"> +<a name="Hollerith-constants-support"></a> +<div class="header"> +<p> +Next: <a href="Character-conversion.html#Character-conversion" accesskey="n" rel="next">Character conversion</a>, Previous: <a href="Implicitly-convert-LOGICAL-and-INTEGER-values.html#Implicitly-convert-LOGICAL-and-INTEGER-values" accesskey="p" rel="previous">Implicitly convert LOGICAL and INTEGER values</a>, Up: <a href="Extensions-implemented-in-GNU-Fortran.html#Extensions-implemented-in-GNU-Fortran" accesskey="u" rel="up">Extensions implemented in GNU Fortran</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p> +</div> +<hr> +<a name="Hollerith-constants-support-1"></a> +<h4 class="subsection">5.1.14 Hollerith constants support</h4> +<a name="index-Hollerith-constants"></a> + +<p>GNU Fortran supports Hollerith constants in assignments, <code>DATA</code> +statements, function and subroutine arguments. A Hollerith constant is +written as a string of characters preceded by an integer constant +indicating the character count, and the letter <code>H</code> or +<code>h</code>, and stored in bytewise fashion in a numeric (<code>INTEGER</code>, +<code>REAL</code>, or <code>COMPLEX</code>), <code>LOGICAL</code> or <code>CHARACTER</code> variable. +The constant will be padded with spaces or truncated to fit the size of +the variable in which it is stored. +</p> +<p>Examples of valid uses of Hollerith constants: +</p><div class="smallexample"> +<pre class="smallexample"> complex*16 x(2) + data x /16Habcdefghijklmnop, 16Hqrstuvwxyz012345/ + x(1) = 16HABCDEFGHIJKLMNOP + call foo (4h abc) +</pre></div> + +<p>Examples of Hollerith constants: +</p><div class="smallexample"> +<pre class="smallexample"> integer*4 a + a = 0H ! Invalid, at least one character is needed. + a = 4HAB12 ! Valid + a = 8H12345678 ! Valid, but the Hollerith constant will be truncated. + a = 3Hxyz ! Valid, but the Hollerith constant will be padded. +</pre></div> + +<p>In general, Hollerith constants were used to provide a rudimentary +facility for handling character strings in early Fortran compilers, +prior to the introduction of <code>CHARACTER</code> variables in Fortran 77; +in those cases, the standard-compliant equivalent is to convert the +program to use proper character strings. On occasion, there may be a +case where the intent is specifically to initialize a numeric variable +with a given byte sequence. In these cases, the same result can be +obtained by using the <code>TRANSFER</code> statement, as in this example. +</p><div class="smallexample"> +<pre class="smallexample"> integer(kind=4) :: a + a = transfer ("abcd", a) ! equivalent to: a = 4Habcd +</pre></div> + +<p>The use of the <samp>-fdec</samp> option extends support of Hollerith constants +to comparisons: +</p><div class="smallexample"> +<pre class="smallexample"> integer*4 a + a = 4hABCD + if (a .ne. 4habcd) then + write(*,*) "no match" + end if +</pre></div> + +<p>Supported types are numeric (<code>INTEGER</code>, <code>REAL</code>, or <code>COMPLEX</code>), +and <code>CHARACTER</code>. +</p> +<hr> +<div class="header"> +<p> +Next: <a href="Character-conversion.html#Character-conversion" accesskey="n" rel="next">Character conversion</a>, Previous: <a href="Implicitly-convert-LOGICAL-and-INTEGER-values.html#Implicitly-convert-LOGICAL-and-INTEGER-values" accesskey="p" rel="previous">Implicitly convert LOGICAL and INTEGER values</a>, Up: <a href="Extensions-implemented-in-GNU-Fortran.html#Extensions-implemented-in-GNU-Fortran" accesskey="u" rel="up">Extensions implemented in GNU Fortran</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p> +</div> + + + +</body> +</html> |