Editing Reduce (computer algebra system) (section)

==== Conditional statements: if ... then ... else ====
The conditional statement has the form
<div class="center" style="width: auto; margin-left: auto; margin-right: auto;">
<code>if</code> ''boolean expression'' <code>then</code> ''statement''
</div>
which can optionally be followed by
<div class="center" style="width: auto; margin-left: auto; margin-right: auto;">
<code>else</code> ''statement''
</div>
For example, the following conditional statement ensures that the value of <math>n</math>, assumed to be numerical, is positive. (It effectively implements the [[Absolute value (algebra)|absolute value]] function.)
<syntaxhighlight lang="octave">
if n < 0 then n := -n
</syntaxhighlight>
The following conditional statement, used as an expression, avoids an error that would be caused by dividing by 0.
<syntaxhighlight lang="octave">
recip_x := if x = 0 then infinity else 1/x
</syntaxhighlight>