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<a name="Hollerith-constants-support"></a>
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Next: <a href="Cray-pointers.html#Cray-pointers" accesskey="n" rel="next">Cray pointers</a>, Previous: <a href="Implicitly-convert-LOGICAL-and-INTEGER-values.html#Implicitly-convert-LOGICAL-and-INTEGER-values" accesskey="p" rel="prev">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>
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<a name="Hollerith-constants-support-1"></a>
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<h4 class="subsection">6.1.13 Hollerith constants support</h4>
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<a name="index-Hollerith-constants"></a>
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<p>GNU Fortran supports Hollerith constants in assignments, function
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arguments, and <code>DATA</code> and <code>ASSIGN</code> statements. A Hollerith
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constant is written as a string of characters preceded by an integer
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constant indicating the character count, and the letter <code>H</code> or
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<code>h</code>, and stored in bytewise fashion in a numeric (<code>INTEGER</code>,
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<code>REAL</code>, or <code>complex</code>) or <code>LOGICAL</code> variable. The
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constant will be padded or truncated to fit the size of the variable in
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which it is stored.
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</p>
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<p>Examples of valid uses of Hollerith constants:
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</p><div class="smallexample">
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<pre class="smallexample"> complex*16 x(2)
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data x /16Habcdefghijklmnop, 16Hqrstuvwxyz012345/
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x(1) = 16HABCDEFGHIJKLMNOP
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call foo (4h abc)
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</pre></div>
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<p>Invalid Hollerith constants examples:
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</p><div class="smallexample">
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<pre class="smallexample"> integer*4 a
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a = 8H12345678 ! Valid, but the Hollerith constant will be truncated.
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a = 0H ! At least one character is needed.
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</pre></div>
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<p>In general, Hollerith constants were used to provide a rudimentary
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facility for handling character strings in early Fortran compilers,
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prior to the introduction of <code>CHARACTER</code> variables in Fortran 77;
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in those cases, the standard-compliant equivalent is to convert the
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program to use proper character strings. On occasion, there may be a
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case where the intent is specifically to initialize a numeric variable
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with a given byte sequence. In these cases, the same result can be
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obtained by using the <code>TRANSFER</code> statement, as in this example.
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</p><div class="smallexample">
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<pre class="smallexample"> INTEGER(KIND=4) :: a
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a = TRANSFER ("abcd", a) ! equivalent to: a = 4Habcd
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</pre></div>
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