Editing APL (programming language) (section)

==== ''Pick 6'' lottery numbers ====
This following immediate-mode expression generates a typical set of ''Pick 6'' [[lottery]] numbers: six [[pseudo-random]] [[integer]]s ranging from 1 to 40, ''guaranteed non-repeating'', and displays them sorted in ascending order:

<syntaxhighlight lang="apl">
x[⍋x←6?40]
</syntaxhighlight>

The above does a lot, concisely, although it may seem complex to a new [[wiktionary:APLer|APLer]]. It combines the following APL ''functions'' (also called ''primitives''<ref>{{cite web|last1=MicroAPL|title=APL Primitives |url=http://www.microapl.co.uk/apl_help/ch_020_020.htm |website=www.microapl.co.uk |publisher=MicroAPL |access-date=January 11, 2015}}</ref> and ''glyphs''<ref>{{cite web |title=APL Font – Extra APL Glyphs |website=wiki.nars2000.org |url=http://wiki.nars2000.org/index.php/APL_Font |publisher=NARS2000 |access-date=January 11, 2015}}</ref>):
* The first to be executed (APL executes from rightmost to leftmost) is dyadic function <code>?</code> (named <code>deal</code> when dyadic) that returns a [[array data structure|vector]] consisting of a select number (left argument: 6 in this case) of random integers ranging from 1 to a specified maximum (right argument: 40 in this case), which, if said maximum ≥ vector length, is guaranteed to be non-repeating; thus, generate/create 6 random integers ranging from 1 to 40.<ref>{{cite web |last1=Fox |first1=Ralph L. |title=Systematically Random Numbers |publisher=SIGAPL |url=http://www.sigapl.org/article1.php |website=www.sigapl.org |access-date=January 11, 2015}}</ref>
* This vector is then ''assigned'' (<code>←</code>) to the variable <code>x</code>, because it is needed later.
* This vector is then ''sorted'' in ascending order by a monadic <code>⍋</code> function, which has as its right argument everything to the right of it up to the next unbalanced ''close-bracket'' or close-parenthesis. The result of <code>⍋</code> is the indices that will put its argument into ascending order.
* Then the output of <code>⍋</code> is used to index the variable <code>x</code>, which we saved earlier for this purpose, thereby selecting its items in ''ascending'' sequence.

Since there is no function to the left of the left-most x to tell APL what to do with the result, it simply outputs it to the display (on a single line, separated by spaces) without needing any explicit instruction to do that.

<code>?</code> also has a monadic equivalent called <code>roll</code>, which simply returns one random integer between 1 and its sole operand [to the right of it], inclusive. Thus, a [[role-playing game]] program might use the expression <code>?20</code> to roll a twenty-sided die.