Re: Unhappy returns

It is worth noting, however, that, contrary to map, grep evaluates its second argument in scalar context:

And contrary to grep and map, foreach evaluates its body in void context:

$ perl
sub ctx { print wantarray ? "list" : defined wantarray ? "scalar" : "v
+oid" }
@x = (1);
print "map:";
map ctx, @x;
print "\ngrep:";
grep ctx, @x;
print "\nfor:";
ctx for @x;
__END__
map:list
grep:scalar
for:void
[download]

Comment on Re: Unhappy returns Download Code

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Re^2: Unhappy returns by thor (Priest) on Oct 10, 2005 at 11:59 UTC
And contrary to grep and map, foreach evaluates its body in void context Isn't the comparison a little unfair? map and grep are operators, whereas for is a looping construct thor `Feel the white light, the light within Be your own disciple, fan the sparks of will For all of us waiting, your kingdom will come`	[reply]
Re^3: Unhappy returns by Perl Mouse (Chaplain) on Oct 10, 2005 at 12:53 UTC
Well, map and grep are usually seen as functions, but there's no denying that both map and grep are looping constructs. But ultimely, what is the difference between an operator, a function or a syntax construct from a programmers aspect of view (other than using it to answer "where do I find this in the manual")? Would you code differently if map or grep were reclassified as a syntax or looping construct, or foreach as a function? `Perl --((8:>*`	[reply]
Re^4: Unhappy returns by Aristotle (Chancellor) on Oct 10, 2005 at 14:33 UTC
The difference is that `foreach` is a statement, and as such does not return anything. The context in which its body is evaluated is therefore never of any interest, any more than it is of interest which context the body of an `if` or `while` is evaluated in. map and grep OTOH are expressions and do return something; which means context is paramount. Makeshifts last the longest.	[reply]
Re^5: Unhappy returns by ysth (Canon) on Oct 10, 2005 at 15:23 UTC
Re^6: Unhappy returns by Aristotle (Chancellor) on Oct 10, 2005 at 15:30 UTC
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Re^6: Unhappy returns by sauoq (Abbot) on Oct 10, 2005 at 17:01 UTC
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