1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
|
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<!-- Created by GNU Texinfo 5.2, http://www.gnu.org/software/texinfo/ -->
<head>
<title>GNU Octave: Built-in Data Types</title>
<meta name="description" content="GNU Octave: Built-in Data Types">
<meta name="keywords" content="GNU Octave: Built-in Data Types">
<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="Concept-Index.html#Concept-Index" rel="index" title="Concept Index">
<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
<link href="Data-Types.html#Data-Types" rel="up" title="Data Types">
<link href="Numeric-Objects.html#Numeric-Objects" rel="next" title="Numeric Objects">
<link href="Data-Types.html#Data-Types" rel="prev" title="Data Types">
<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="Built_002din-Data-Types"></a>
<div class="header">
<p>
Next: <a href="User_002ddefined-Data-Types.html#User_002ddefined-Data-Types" accesskey="n" rel="next">User-defined Data Types</a>, Up: <a href="Data-Types.html#Data-Types" accesskey="u" rel="up">Data Types</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p>
</div>
<hr>
<a name="Built_002din-Data-Types-1"></a>
<h3 class="section">3.1 Built-in Data Types</h3>
<a name="index-data-types_002c-built_002din"></a>
<a name="index-built_002din-data-types"></a>
<p>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>
<p>The data type of a variable can be determined and changed through the
use of the following functions.
</p>
<a name="XREFclass"></a><dl>
<dt><a name="index-class"></a>Function File: <em><var>classname</var> =</em> <strong>class</strong> <em>(<var>obj</var>)</em></dt>
<dt><a name="index-class-1"></a>Function File: <em></em> <strong>class</strong> <em>(<var>s</var>, <var>id</var>)</em></dt>
<dt><a name="index-class-2"></a>Function File: <em></em> <strong>class</strong> <em>(<var>s</var>, <var>id</var>, <var>p</var>, …)</em></dt>
<dd><p>Return the class of the object <var>obj</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>
<p><strong>See also:</strong> <a href="Data-Types.html#XREFtypeinfo">typeinfo</a>, <a href="#XREFisa">isa</a>.
</p></dd></dl>
<a name="XREFisa"></a><dl>
<dt><a name="index-isa"></a>Function File: <em></em> <strong>isa</strong> <em>(<var>obj</var>, <var>classname</var>)</em></dt>
<dd><p>Return true if <var>obj</var> is an object from the class <var>classname</var>.
</p>
<p><var>classname</var> may also be one of the following class categories:
</p>
<dl compact="compact">
<dt><code>"float"</code></dt>
<dd><p>Floating point value comprising classes <code>"double"</code> and
<code>"single"</code>.
</p>
</dd>
<dt><code>"integer"</code></dt>
<dd><p>Integer value comprising classes (u)int8, (u)int16, (u)int32, (u)int64.
</p>
</dd>
<dt><code>"numeric"</code></dt>
<dd><p>Numeric value comprising either a floating point or integer value.
</p></dd>
</dl>
<p><strong>See also:</strong> <a href="#XREFclass">class</a>, <a href="Data-Types.html#XREFtypeinfo">typeinfo</a>.
</p></dd></dl>
<a name="XREFcast"></a><dl>
<dt><a name="index-cast"></a>Function File: <em></em> <strong>cast</strong> <em>(<var>val</var>, <var>type</var>)</em></dt>
<dd><p>Convert <var>val</var> to data type <var>type</var>.
</p>
<p><strong>See also:</strong> <a href="Integer-Data-Types.html#XREFint8">int8</a>, <a href="Integer-Data-Types.html#XREFuint8">uint8</a>, <a href="Integer-Data-Types.html#XREFint16">int16</a>, <a href="Integer-Data-Types.html#XREFuint16">uint16</a>, <a href="Integer-Data-Types.html#XREFint32">int32</a>, <a href="Integer-Data-Types.html#XREFuint32">uint32</a>, <a href="Integer-Data-Types.html#XREFint64">int64</a>, <a href="Integer-Data-Types.html#XREFuint64">uint64</a>, <a href="Numeric-Data-Types.html#XREFdouble">double</a>.
</p></dd></dl>
<a name="XREFtypecast"></a><dl>
<dt><a name="index-typecast"></a>Built-in Function: <em></em> <strong>typecast</strong> <em>(<var>x</var>, <var>class</var>)</em></dt>
<dd><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:
</p>
<div class="example">
<pre class="example">"logical"
"char"
"int8"
"int16"
"int32"
"int64"
"uint8"
"uint16"
"uint32"
"uint64"
"double"
"single"
"double complex"
"single complex"
</pre></div>
<p>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.
<code>"logical"</code> 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>
<p>An example of the use of typecast on a little-endian machine is
</p>
<div class="example">
<pre class="example"><var>x</var> = uint16 ([1, 65535]);
typecast (<var>x</var>, "uint8")
⇒ [ 1, 0, 255, 255]
</pre></div>
<p><strong>See also:</strong> <a href="#XREFcast">cast</a>, <a href="#XREFbitunpack">bitunpack</a>, <a href="#XREFbitpack">bitpack</a>, <a href="#XREFswapbytes">swapbytes</a>.
</p></dd></dl>
<a name="XREFswapbytes"></a><dl>
<dt><a name="index-swapbytes"></a>Function File: <em></em> <strong>swapbytes</strong> <em>(<var>x</var>)</em></dt>
<dd><p>Swap the byte order on values, converting from little endian to big
endian and vice versa. For example:
</p>
<div class="example">
<pre class="example">swapbytes (uint16 (1:4))
⇒ [ 256 512 768 1024]
</pre></div>
<p><strong>See also:</strong> <a href="#XREFtypecast">typecast</a>, <a href="#XREFcast">cast</a>.
</p></dd></dl>
<a name="XREFbitpack"></a><dl>
<dt><a name="index-bitpack"></a>Built-in Function: <em><var>y</var> =</em> <strong>bitpack</strong> <em>(<var>x</var>, <var>class</var>)</em></dt>
<dd><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:
</p>
<div class="example">
<pre class="example">"char"
"int8"
"int16"
"int32"
"int64"
"uint8"
"uint16"
"uint32"
"uint64"
"double"
"single"
</pre></div>
<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.
</p>
<p><strong>See also:</strong> <a href="#XREFbitunpack">bitunpack</a>, <a href="#XREFtypecast">typecast</a>.
</p></dd></dl>
<a name="XREFbitunpack"></a><dl>
<dt><a name="index-bitunpack"></a>Built-in Function: <em><var>y</var> =</em> <strong>bitunpack</strong> <em>(<var>x</var>)</em></dt>
<dd><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:
</p>
<div class="example">
<pre class="example">"char"
"int8"
"int16"
"int32"
"int64"
"uint8"
"uint16"
"uint32"
"uint64"
"double"
"single"
</pre></div>
<p>The result is a row vector if <var>x</var> is a row vector; otherwise, it is a
column vector.
</p>
<p><strong>See also:</strong> <a href="#XREFbitpack">bitpack</a>, <a href="#XREFtypecast">typecast</a>.
</p></dd></dl>
<table class="menu" border="0" cellspacing="0">
<tr><td align="left" valign="top">• <a href="Numeric-Objects.html#Numeric-Objects" accesskey="1">Numeric Objects</a>:</td><td> </td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">• <a href="Missing-Data.html#Missing-Data" accesskey="2">Missing Data</a>:</td><td> </td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">• <a href="String-Objects.html#String-Objects" accesskey="3">String Objects</a>:</td><td> </td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">• <a href="Data-Structure-Objects.html#Data-Structure-Objects" accesskey="4">Data Structure Objects</a>:</td><td> </td><td align="left" valign="top">
</td></tr>
<tr><td align="left" valign="top">• <a href="Cell-Array-Objects.html#Cell-Array-Objects" accesskey="5">Cell Array Objects</a>:</td><td> </td><td align="left" valign="top">
</td></tr>
</table>
<hr>
<div class="header">
<p>
Next: <a href="User_002ddefined-Data-Types.html#User_002ddefined-Data-Types" accesskey="n" rel="next">User-defined Data Types</a>, Up: <a href="Data-Types.html#Data-Types" accesskey="u" rel="up">Data Types</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p>
</div>
</body>
</html>
|
