RE: [perl #130038] Builtin variable for loop index in foreach

Dave Mitchell wrote:

>For ranges, e.g. (1..10) and ('a'..'z'), it only records the current value and the last value.

But for numeric ranges, if you know the current value it is just a subtraction to find its index.
For string ranges like 'aa'..'zz' it is trickier but still possible.  So fetching $# could do that?

>give $# get magic that searches the context stack for a loop context,
>then retrieves the current loop index stored in there. That wouldn't
>slow down normal loops, but accessing $# itself might be quite slow.

I think it would still be faster than the equivalent handwritten code using an $i variable, though?

My concern would be whether in all cases 'searching the context stack for a loop'
gives exactly the same semantics as we currently have for $_ in nested loops.
Or whether the odd differences are not worth worrying about.

-- 
Ed Avis <eda@waniasset.com>

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• [perl #130038] Builtin variable for loop index in foreach by Ed Avis
• Re: [perl #130038] Builtin variable for loop index in foreach by Dave Mitchell
• Re: [perl #130038] Builtin variable for loop index in foreach by Aristotle Pagaltzis
• Re: [perl #130038] Builtin variable for loop index in foreach by Kent Fredric
• Re: [perl #130038] Builtin variable for loop index in foreach by Dave Mitchell
• Re: [perl #130038] Builtin variable for loop index in foreach by Dave Mitchell
• Re: [perl #130038] Builtin variable for loop index in foreach by Kent Fredric
• Re: [perl #130038] Builtin variable for loop index in foreach by Kent Fredric
• [perl #130038] Builtin variable for loop index in foreach by Hugo van der Sanden via RT
• Re: [perl #130038] Builtin variable for loop index in foreach by Zefram
• Re: [perl #130038] Builtin variable for loop index in foreach by Dave Mitchell
• [perl #130038] Builtin variable for loop index in foreach by Ed Avis via RT
• RE: [perl #130038] Builtin variable for loop index in foreach by Ed Avis
• Re: [perl #130038] Builtin variable for loop index in foreach by demerphq
• Re: [perl #130038] Builtin variable for loop index in foreach by Dave Mitchell
• RE: [perl #130038] Builtin variable for loop index in foreach by Ed Avis