Variable declaration reset: Difference between revisions

=={{header|Factor}}==

Normally you would not use lexical scoping for something like this in Factor. But since it is possible, here we go. Note that:

* Factor doesn't allow you to declare a lexical variable without initializing it.

* Lexical variables are immutable by default. To make a lexical variable mutable, you need to add a <code>!</code> to its declaration.

{{works with|Factor|0.99 2022-04-03}}

<lang factor>USING: kernel math prettyprint sequences ;

[let

{ 1 2 2 3 4 4 5 } :> s

s length <iota> [| i |

i s nth -1 :> ( curr prev! )

i 1 > curr prev = and

[ i . ] when

curr prev!

] each

]</lang>

{{out}}

[none]

To get output, we need to declare <code>prev</code> outside the <code>each</code> quotation.

{{works with|Factor|0.99 2022-04-03}}

<lang factor>USING: kernel math prettyprint sequences ;

[let

{ 1 2 2 3 4 4 5 } -1 :> ( s prev! )

s length <iota> [| i |

i s nth :> curr

i 1 > curr prev = and

[ i . ] when

curr prev!

] each

]</lang>

{{out}}

<pre>

2

5

</pre>

Now compare to how you would normally solve this in Factor, where issues of variables and scope are irrelevant:

{{works with|Factor|0.99 2022-04-03}}

<lang factor>USING: grouping math.vectors prettyprint sequences.extras ;

{ 1 2 2 3 4 4 5 } 2 <clumps> [ all-eq? ] arg-where 1 v+n .</lang>