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<h1>Operators</h1>
In DPUSER, operators are used to combine expressions. There are several
types of operators:
<ul>
<li>
<a href="#assignment">Assignment</a></li>
<li>
<a href="#parentesis">Parentesis</a></li>
<li>
<a href="#ranges">Ranges</a></li>
<li>
<a href="#mathematical">Mathematical</a></li>
<li>
<a href="#boolean">Boolean</a></li>
</ul>
<h2>
<a NAME="assignment"></a>Assignment</h2>
To assign a value to a variable, the assignment operator is used. The general
syntax of an assignment is:
<blockquote><tt>VARIABLE = value</tt>
<br><tt>VARIABLE += value</tt>
<br><tt>...</tt></blockquote>
or, if you wish to assign a value to a subset of a matrix:
<blockquote><tt>VARIABLE[range] = value</tt>
<br><tt>VARIABLE[range] += value</tt>
<br><tt>...</tt></blockquote>
Like in the C programming language, several assignment operators are possible.
<br>
<table CELLSPACING=0 CELLPADDING=0 WIDTH="100%" >
<tr>
<td><b>Operator</b></td>
<td><b>Syntax</b></td>
<td><b>Operands</b></td>
</tr>
<tr>
<td VALIGN=BASELINE NOWRAP>Assignment</td>
<td VALIGN=BASELINE NOWRAP><tt>VARIABLE = value</tt></td>
<td VALIGN=BASELINE>Number, matrix, string, string array</td>
</tr>
<tr>
<td VALIGN=BASELINE NOWRAP>Increment</td>
<td VALIGN=BASELINE NOWRAP><tt>VARIABLE++</tt></td>
<td VALIGN=BASELINE>Number, matrix</td>
</tr>
<tr>
<td VALIGN=BASELINE NOWRAP>Decrement</td>
<td VALIGN=BASELINE NOWRAP><tt>VARIABLE--</tt></td>
<td VALIGN=BASELINE>Number, matrix</td>
</tr>
<tr>
<td VALIGN=BASELINE NOWRAP>Multiplication</td>
<td VALIGN=BASELINE NOWRAP><tt>VARIABLE *= value</tt></td>
<td VALIGN=BASELINE>Number, matrix</td>
</tr>
<tr>
<td VALIGN=BASELINE NOWRAP>Division</td>
<td VALIGN=BASELINE NOWRAP><tt>VARIABLE /= value</tt></td>
<td VALIGN=BASELINE>Number, matrix</td>
</tr>
<tr>
<td VALIGN=BASELINE NOWRAP>Addition</td>
<td VALIGN=BASELINE NOWRAP><tt>VARIABLE += value</tt></td>
<td VALIGN=BASELINE>Number, matrix, string, string array</td>
</tr>
<tr>
<td VALIGN=BASELINE NOWRAP>Subtraction</td>
<td VALIGN=BASELINE NOWRAP><tt>VARIABLE -= value</tt></td>
<td VALIGN=BASELINE>Number, matrix</td>
</tr>
</table>
<p>If the "<tt>+=</tt>" operator is applied to a string array, the string
at the right hand side of the statement will be appended to the string
array.
<br>The assignment operator "<tt>=</tt>" can be used to write a matrix
as a FITS file. The syntax for doing this is <tt>'filename'=matrix</tt>,
i.e. you assign a matrix to a filename, which is in single quotes. Note
that writing FITS files is also possible using the <a href="procedure_writefits.html">writefits</a>
procedure.
<h3>
Examples</h3>
<table CELLSPACING=0 CELLPADDING=0 WIDTH="100%" >
<tr>
<td VALIGN=BASELINE NOWRAP><tt>var = 6</tt></td>
<td VALIGN=BASELINE>creates a new variable named <tt>var</tt> and assigns
a value of 6</td>
</tr>
<tr>
<td VALIGN=BASELINE NOWRAP><tt>'gauss.fits' = gauss(129, 129, 30)</tt></td>
<td VALIGN=BASELINE>writes a 2-dimensional gaussian to a disk file named
<tt>gauss.fits</tt></td>
</tr>
<tr>
<td VALIGN=BASELINE NOWRAP><tt>var[100:200, *]++</tt></td>
<td VALIGN=BASELINE>Increments elements 100 through 200 in the first dimension
and all elements in the second dimension</td>
</tr>
</table>
<h2>
<a NAME="parentesis"></a>Parentesis</h2>
Parentesis are used in two ways: To enclose arguments to a function, and
to group expressions. Parentesis can be used to override operator precedence.
<h3>
Examples</h3>
<table CELLSPACING=0 CELLPADDING=0 WIDTH="100%" >
<tr>
<td VALIGN=BASELINE NOWRAP><tt>print sin(pi())</tt></td>
<td VALIGN=BASELINE WIDTH="100%">prints out the sine of pi</td>
</tr>
<tr>
<td VALIGN=BASELINE NOWRAP><tt>var = 2 + 3 * 5 </tt></td>
<td VALIGN=BASELINE>yields 17</td>
</tr>
<tr>
<td VALIGN=BASELINE NOWRAP><tt>var = (2 + 3) * 5</tt></td>
<td VALIGN=BASELINE>yields 25</td>
</tr>
</table>
<h2>
<a NAME="ranges"></a>Ranges</h2>
With ranges, you can create matrices and string arrays, and you can access
subscripts of arrays. To access a single elements of a matrix, supply the
coordinates like <tt>[5,3]</tt>. To access a range, give the inclusive
range, separated by a colon like <tt>[100:300, 50:60]</tt>. You can use
the asterisk (<tt>*</tt>) to access all elements in an axes. Ranges in
DPUSER are 1-based like in fortran. The arguments in a range can be the
result of an expression.
<h3>
Examples</h3>
<table CELLSPACING=0 CELLPADDING=0 WIDTH="100%" >
<tr>
<td VALIGN=BASELINE NOWRAP><tt>mvar = [1, sin(pi()), 3+5]</tt></td>
<td>creates a 1-dimensional matrix with the values 1, 0, 8</td>
</tr>
<tr>
<td VALIGN=BASELINE NOWRAP><tt>nvar = [-3600:3600] / 10</tt></td>
<td>creates a 1D matrix with the values -360, -359.9, ..., 360</td>
</tr>
<tr>
<td VALIGN=BASELINE NOWRAP><tt>svar = ["test", "string"]</tt></td>
<td>creates a string array with 2 elements</td>
</tr>
<tr>
<td VALIGN=BASELINE NOWRAP><tt>print mvar[2]</tt></td>
<td>prints the second element of <tt>mvar</tt>, which is 0</td>
</tr>
<tr>
<td VALIGN=BASELINE NOWRAP><tt>print svar[1]</tt></td>
<td>prints out "test"</td>
</tr>
<tr>
<td VALIGN=BASELINE NOWRAP><tt>print svar[2][strlen(svar[2])]</tt></td>
<td VALIGN=BASELINE>prints out the last character of the second element
of svar, which is a "g"</td>
</tr>
<tr>
<td VALIGN=BASELINE NOWRAP><tt>newvar = nvar[3601:3700]</tt></td>
<td>creates a new matrix variable with 100 elements and assigns the values
0, 0.1, ..., 9.9</td>
</tr>
</table>
<h2>
<a NAME="mathematical"></a>Mathematical operators</h2>
The basic mathematical operators are used in DPUSER. Depending on the type
of associated variables, different actions (described below) are taken.
If a matrix is combined with another matrix or a number, the result will be
a matrix in which the operation is performed on each element. The available
operators in precedence order are:
<br>
<table CELLSPACING=0 CELLPADDING=0 WIDTH="100%" >
<tr>
<td WIDTH="20%"><b>Operator</b></td>
<td WIDTH="10%"><b>Syntax</b></td>
<td WIDTH="30%"><b>Arguments</b></td>
<td WIDTH="40%"><b>Return Value</b></td>
</tr>
<tr>
<td VALIGN=BASELINE>Exponentation</td>
<td VALIGN=BASELINE><b><tt>x ^ y</tt></b></td>
<td VALIGN=BASELINE>Number, Matrix</td>
<td>Number if both x and y are numbers
<br>Matrix if either x or y is a matrix</td>
</tr>
<tr>
<td></td>
<td></td>
<td></td>
<td></td>
</tr>
<tr>
<td></td>
<td></td>
<td></td>
<td></td>
</tr>
<tr>
<td VALIGN=BASELINE>Multiplication</td>
<td VALIGN=BASELINE><b><tt>x * y</tt></b></td>
<td VALIGN=BASELINE>Number, Matrix</td>
<td>Number if both x and y are numbers
<br>Matrix if either x or y is a matrix</td>
</tr>
<tr>
<td></td>
<td></td>
<td></td>
<td></td>
</tr>
<tr>
<td VALIGN=BASELINE>Matrix multiplication</td>
<td VALIGN=BASELINE><b><tt>x # y</tt></b></td>
<td VALIGN=BASELINE>Matrix or vector</td>
<td>Matrix</td>
</tr>
<tr>
<td></td>
<td></td>
<td></td>
<td></td>
</tr>
<tr>
<td VALIGN=BASELINE>Division</td>
<td VALIGN=BASELINE><b><tt>x / y</tt></b></td>
<td VALIGN=BASELINE>Number, Matrix</td>
<td>Number if both x and y are numbers
<br>Matrix if either x or y is a matrix</td>
</tr>
<tr>
<td></td>
<td></td>
<td></td>
<td></td>
</tr>
<tr>
<td VALIGN=BASELINE>Modulus</td>
<td VALIGN=BASELINE><b><tt>x % y</tt></b></td>
<td VALIGN=BASELINE>Integer number</td>
<td>Integer number
</tr>
<tr>
<td VALIGN=BASELINE>Addition</td>
<td VALIGN=BASELINE><b><tt>x + y</tt></b></td>
<td VALIGN=BASELINE>Number, Matrix</td>
<td>Number if both x and y are numbers
<br>Matrix if either x or y is a matrix</td>
</tr>
<tr>
<td></td>
<td></td>
<td VALIGN=BASELINE>Number, String</td>
<td>String if either x or y is a string</td>
</tr>
<tr>
<td></td>
<td></td>
<td VALIGN=BASELINE>String, String array</td>
<td>String array if either x or y is a string array</td>
</tr>
<tr>
<td VALIGN=BASELINE>Subtraction</td>
<td VALIGN=BASELINE><b><tt>x - y</tt></b></td>
<td VALIGN=BASELINE>Number, Matrix</td>
<td>Number if both x and y are numbers
<br>Matrix if either x or y is a matrix</td>
</tr>
</table>
<h2>
<a NAME="boolean"></a>Boolean operators</h2>
Conditional statements can be given using the following operators. The
list is in precedence order:
<br>
<table CELLSPACING=0 CELLPADDING=0 WIDTH="100%" >
<tr>
<td WIDTH="30%"><b>Operator</b></td>
<td WIDTH="10%"><b>Syntax</b></td>
<td WIDTH="20%"><b>Arguments</b></td>
<td WIDTH="40%"><b>Return Value</b></td>
</tr>
<tr>
<td>Not</td>
<td><b><tt>!x</tt></b></td>
<td>Boolean</td>
<td>Boolean</td>
</tr>
<tr>
<td>Not equals</td>
<td><b><tt>x != y</tt></b></td>
<td>Number, String</td>
<td>Boolean</td>
</tr>
<tr>
<td>Equals</td>
<td><b><tt>x == y</tt></b></td>
<td>Number, String</td>
<td>Boolean</td>
</tr>
<tr>
<td>Greater than</td>
<td><b><tt>x > y</tt></b></td>
<td>Number, String</td>
<td>Boolean</td>
</tr>
<tr>
<td>Greater or equal</td>
<td><b><tt>x >= y</tt></b></td>
<td>Number, String</td>
<td>Boolean</td>
</tr>
<tr>
<td>Less than</td>
<td><b><tt>x < y</tt></b></td>
<td>Number, String</td>
<td>Boolean</td>
</tr>
<tr>
<td>Less than or equal to</td>
<td><b><tt>x <= y</tt></b></td>
<td>Number, String</td>
<td>Boolean</td>
</tr>
<tr>
<td></td>
<td></td>
<td></td>
<td></td>
</tr>
<tr>
<td>And</td>
<td><b><tt>x && y</tt></b></td>
<td>Boolean</td>
<td>Boolean</td>
</tr>
<tr>
<td>Or</td>
<td><b><tt>x || y</tt></b></td>
<td>Boolean</td>
<td>Boolean</td>
</tr>
</table>
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Copyright © Thomas Ott ---- DPUSER - The Next Generation 3.3 (Rev. )
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