APL2C: Difference between revisions

[[Control structure]]s could be written using the <syntaxhighlight lang=apl inline>∇</syntaxhighlight> character, which was not used for [[defined function|function definition]] because this was initiated with editor interaction rather than source code. All control structures were written with an opening <syntaxhighlight lang=apl inline>∇</syntaxhighlight> followed by an expression, and closed with <syntaxhighlight lang=apl inline>∇</syntaxhighlight> alone. For example, the following structure doubles <syntaxhighlight lang=apl inline>X</syntaxhighlight> if it's less than 3.

If the expression evaluates to a non-negative number, the enclosed code is repeated that many times. A negative number indicates to repeat a number of times equal to the absolute value, but re-evaluate the controlling expression afterwards, allowing "while" to be implemented. A vector indicates counts for multiple sections, which are each preceded with a label-less <syntaxhighlight lang=apl inline>:</syntaxhighlight>, allowing "if-else" and "select" forms.