<html lang="en"> <head> <title>Built-in Data Types - GNU Octave</title> <meta http-equiv="Content-Type" content="text/html"> <meta name="description" content="GNU Octave"> <meta name="generator" content="makeinfo 4.13"> <link title="Top" rel="start" href="index.html#Top"> <link rel="up" href="Data-Types.html#Data-Types" title="Data Types"> <link rel="next" href="User_002ddefined-Data-Types.html#User_002ddefined-Data-Types" title="User-defined Data Types"> <link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage"> <meta http-equiv="Content-Style-Type" content="text/css"> <style type="text/css"><!-- pre.display { font-family:inherit } pre.format { font-family:inherit } pre.smalldisplay { font-family:inherit; font-size:smaller } pre.smallformat { font-family:inherit; font-size:smaller } pre.smallexample { font-size:smaller } pre.smalllisp { font-size:smaller } span.sc { font-variant:small-caps } span.roman { font-family:serif; font-weight:normal; } span.sansserif { font-family:sans-serif; font-weight:normal; } --></style> </head> <body> <div class="node"> <a name="Built-in-Data-Types"></a> <a name="Built_002din-Data-Types"></a> <p> Next: <a rel="next" accesskey="n" href="User_002ddefined-Data-Types.html#User_002ddefined-Data-Types">User-defined Data Types</a>, Up: <a rel="up" accesskey="u" href="Data-Types.html#Data-Types">Data Types</a> <hr> </div> <h3 class="section">3.1 Built-in Data Types</h3> <p><a name="index-data-types_002c-built_002din-199"></a><a name="index-built_002din-data-types-200"></a> The standard built-in data types are real and complex scalars and matrices, ranges, character strings, a data structure type, and cell arrays. Additional built-in data types may be added in future versions. If you need a specialized data type that is not currently provided as a built-in type, you are encouraged to write your own user-defined data type and contribute it for distribution in a future release of Octave. <p>The data type of a variable can be determined and changed through the use of the following functions. <!-- class src/ov-class.cc --> <p><a name="doc_002dclass"></a> <div class="defun"> — Built-in Function: <b>class</b> (<var>expr</var>)<var><a name="index-class-201"></a></var><br> — Built-in Function: <b>class</b> (<var>s, id</var>)<var><a name="index-class-202"></a></var><br> — Built-in Function: <b>class</b> (<var>s, id, p, <small class="dots">...</small></var>)<var><a name="index-class-203"></a></var><br> <blockquote><p>Return the class of the expression <var>expr</var> or create a class with fields from structure <var>s</var> and name (string) <var>id</var>. Additional arguments name a list of parent classes from which the new class is derived. </p></blockquote></div> <!-- isa scripts/general/isa.m --> <p><a name="doc_002disa"></a> <div class="defun"> — Function File: <b>isa</b> (<var>obj, class</var>)<var><a name="index-isa-204"></a></var><br> <blockquote><p>Return true if <var>obj</var> is an object from the class <var>class</var>. <!-- Texinfo @sp should work but in practice produces ugly results for HTML. --> <!-- A simple blank line produces the correct behavior. --> <!-- @sp 1 --> <p class="noindent"><strong>See also:</strong> <a href="doc_002dclass.html#doc_002dclass">class</a>, <a href="doc_002dtypeinfo.html#doc_002dtypeinfo">typeinfo</a>. </p></blockquote></div> <!-- cast scripts/miscellaneous/cast.m --> <p><a name="doc_002dcast"></a> <div class="defun"> — Function File: <b>cast</b> (<var>val, type</var>)<var><a name="index-cast-205"></a></var><br> <blockquote><p>Convert <var>val</var> to data type <var>type</var>. <!-- Texinfo @sp should work but in practice produces ugly results for HTML. --> <!-- A simple blank line produces the correct behavior. --> <!-- @sp 1 --> <p class="noindent"><strong>See also:</strong> <a href="doc_002dint8.html#doc_002dint8">int8</a>, <a href="doc_002duint8.html#doc_002duint8">uint8</a>, <a href="doc_002dint16.html#doc_002dint16">int16</a>, <a href="doc_002duint16.html#doc_002duint16">uint16</a>, <a href="doc_002dint32.html#doc_002dint32">int32</a>, <a href="doc_002duint32.html#doc_002duint32">uint32</a>, <a href="doc_002dint64.html#doc_002dint64">int64</a>, <a href="doc_002duint64.html#doc_002duint64">uint64</a>, <a href="doc_002ddouble.html#doc_002ddouble">double</a>. </p></blockquote></div> <!-- typecast src/DLD-FUNCTIONS/typecast.cc --> <p><a name="doc_002dtypecast"></a> <div class="defun"> — Loadable Function: <b>typecast</b> (<var>x, class</var>)<var><a name="index-typecast-206"></a></var><br> <blockquote><p>Return a new array <var>y</var> resulting from interpreting the data of <var>x</var> in memory as data of the numeric class <var>class</var>. Both the class of <var>x</var> and <var>class</var> must be one of the built-in numeric classes: <pre class="example"> "logical" "char" "int8" "int16" "int32" "int64" "uint8" "uint16" "uint32" "uint64" "double" "single" "double complex" "single complex" </pre> <p class="noindent">the last two are reserved for <var>class</var>; they indicate that a complex-valued result is requested. Complex arrays are stored in memory as consecutive pairs of real numbers. The sizes of integer types are given by their bit counts. Both logical and char are typically one byte wide; however, this is not guaranteed by C++. If your system is IEEE conformant, single and double should be 4 bytes and 8 bytes wide, respectively. "logical" is not allowed for <var>class</var>. If the input is a row vector, the return value is a row vector, otherwise it is a column vector. If the bit length of <var>x</var> is not divisible by that of <var>class</var>, an error occurs. <p>An example of the use of typecast on a little-endian machine is <pre class="example"> <var>x</var> = uint16 ([1, 65535]); typecast (<var>x</var>, 'uint8') ⇒ [ 1, 0, 255, 255] </pre> <!-- Texinfo @sp should work but in practice produces ugly results for HTML. --> <!-- A simple blank line produces the correct behavior. --> <!-- @sp 1 --> <p class="noindent"><strong>See also:</strong> <a href="doc_002dcast.html#doc_002dcast">cast</a>, <a href="doc_002dbitunpack.html#doc_002dbitunpack">bitunpack</a>, <a href="doc_002dbitpack.html#doc_002dbitpack">bitpack</a>, <a href="doc_002dswapbytes.html#doc_002dswapbytes">swapbytes</a>. </p></blockquote></div> <!-- swapbytes scripts/miscellaneous/swapbytes.m --> <p><a name="doc_002dswapbytes"></a> <div class="defun"> — Function File: <b>swapbytes</b> (<var>x</var>)<var><a name="index-swapbytes-207"></a></var><br> <blockquote><p>Swap the byte order on values, converting from little endian to big endian and vice versa. For example: <pre class="example"> swapbytes (uint16 (1:4)) ⇒ [ 256 512 768 1024] </pre> <!-- Texinfo @sp should work but in practice produces ugly results for HTML. --> <!-- A simple blank line produces the correct behavior. --> <!-- @sp 1 --> <p class="noindent"><strong>See also:</strong> <a href="doc_002dtypecast.html#doc_002dtypecast">typecast</a>, <a href="doc_002dcast.html#doc_002dcast">cast</a>. </p></blockquote></div> <!-- bitpack src/DLD-FUNCTIONS/typecast.cc --> <p><a name="doc_002dbitpack"></a> <div class="defun"> — Loadable Function: <var>y</var> = <b>bitpack</b> (<var>x, class</var>)<var><a name="index-bitpack-208"></a></var><br> <blockquote><p>Return a new array <var>y</var> resulting from interpreting an array <var>x</var> as raw bit patterns for data of the numeric class <var>class</var>. <var>class</var> must be one of the built-in numeric classes: <pre class="example"> "char" "int8" "int16" "int32" "int64" "uint8" "uint16" "uint32" "uint64" "double" "single" </pre> <p>The number of elements of <var>x</var> should be divisible by the bit length of <var>class</var>. If it is not, excess bits are discarded. Bits come in increasing order of significance, i.e., <code>x(1)</code> is bit 0, <code>x(2)</code> is bit 1, etc. The result is a row vector if <var>x</var> is a row vector, otherwise it is a column vector. <!-- Texinfo @sp should work but in practice produces ugly results for HTML. --> <!-- A simple blank line produces the correct behavior. --> <!-- @sp 1 --> <p class="noindent"><strong>See also:</strong> <a href="doc_002dbitunpack.html#doc_002dbitunpack">bitunpack</a>, <a href="doc_002dtypecast.html#doc_002dtypecast">typecast</a>. </p></blockquote></div> <!-- bitunpack src/DLD-FUNCTIONS/typecast.cc --> <p><a name="doc_002dbitunpack"></a> <div class="defun"> — Loadable Function: <var>y</var> = <b>bitunpack</b> (<var>x</var>)<var><a name="index-bitunpack-209"></a></var><br> <blockquote><p>Return an array <var>y</var> corresponding to the raw bit patterns of <var>x</var>. <var>x</var> must belong to one of the built-in numeric classes: <pre class="example"> "char" "int8" "int16" "int32" "int64" "uint8" "uint16" "uint32" "uint64" "double" "single" </pre> <p>The result is a row vector if <var>x</var> is a row vector; otherwise, it is a column vector. <!-- Texinfo @sp should work but in practice produces ugly results for HTML. --> <!-- A simple blank line produces the correct behavior. --> <!-- @sp 1 --> <p class="noindent"><strong>See also:</strong> <a href="doc_002dbitpack.html#doc_002dbitpack">bitpack</a>, <a href="doc_002dtypecast.html#doc_002dtypecast">typecast</a>. </p></blockquote></div> <ul class="menu"> <li><a accesskey="1" href="Numeric-Objects.html#Numeric-Objects">Numeric Objects</a> <li><a accesskey="2" href="Missing-Data.html#Missing-Data">Missing Data</a> <li><a accesskey="3" href="String-Objects.html#String-Objects">String Objects</a> <li><a accesskey="4" href="Data-Structure-Objects.html#Data-Structure-Objects">Data Structure Objects</a> <li><a accesskey="5" href="Cell-Array-Objects.html#Cell-Array-Objects">Cell Array Objects</a> </ul> </body></html>