Closures/Value capture: Difference between revisions

=={{header|Factor}}==

<lang factor>USING: io kernel locals math math.ranges prettyprint sequences ;

! Create a sequence of ten quotations

[let

10 iota [

:> i ! Bind lexical variable i

[ i i * ] ! Push a quotation to calculate i squared

] map :> seq

{ 3 8 } [

dup pprint " squared is " write

seq nth call .

] each

]</lang>

<pre>$ ./factor script.factor

3 squared is 9

8 squared is 64</pre>

The code <code>:> i</code> always binds a new variable. This happens inside a loop, so this program creates 10 different bindings. Each closure <code>[ i i * ]</code> captures a different binding, and remembers a different value.

The wrong way would use <code>f :> i! 10 iota [ i! [ i i * ] ] map :> seq</code> to mutate a single binding. Then the program would print, "3 squared is 81", "8 squared is 81".