Grouping perl foreach values

[Alex Satrapa]

On Tuesday, July 9, 2002, at 11:09 , Michael Still wrote:

> I have a list of value in the form:
>
>   v1;v2;v3;v4;v5;v6;v7;v8;v9
>
> And I want to work through them in sets of three, something like:
>
> foreach($cola, $colb, $colc) ($listofthings){
>   ... do stuff ...
> }

What's important about the groups of three?

Perhaps if there's some data structure there, you should implement it as 
a structure in Perl, and use foreach to iterate over a list of these 
structures?

Otherwise, you don't really want to use foreach anyway, you might have 
luck with something like:

for ($i=0; $i < (scalar(@list)/3); $i++) {
    @sublist = @list[$i * 3 .. $i * 3 + 2];
    # Do stuff with three elements in sublist here
}

But this is probably the wrong tool for the wrong job.  Slightly less 
wrong might be:

while (scalar(@list)) {
	$foo = shift @list;
	$bar = shift @list;
	$baz = shift @list;
	# Do stuff with foo/bar/baz here
}

Though that does assume that your list has (n * 3) items in it, and 
you're going to have trouble if it doesn't.

Get the data structure right, and the code will be self-evident.

Alex
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