How does func2 know the context?

Question

func1(func2);

As we know Perl needs to know the context to evaluate,but in the above case how does func2 know it's in scalar or list context?

I think it will be scalar unless you include a prototype (ala `sub func1($$$)`) for `func1` — Ben Jackson, Jul 29 '11 at 07:51
@Ben Jackson: No, in the absence of a prototype `func2` would be called in list context -- it's part of the *list* of arguments. — Michael Carman, Jul 29 '11 at 13:15

score 5 · Accepted Answer · edited May 23 '17 at 12:04

5

If func1 does not have a prototype (or a @ prototype), it will be list context. If func1 has a prototype of $, then it will be scalar context.

Caveat: please do not use prototypes, they're evil.

edited May 23 '17 at 12:04

Community

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answered Jul 29 '11 at 08:25

Leon Timmermans

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score 2 · Answer 2 · answered Jul 29 '11 at 07:51

2

Apparently. it's list.

$ perl
sub f1 { print "called f1\n" } 
sub f2 { print "called f2\n"; print wantarray ? "list": "scalar"; print "\n"; }
f1(f2);
^d
called f2
list
called f1

Why? That's another question entirely - I assume because function params are implicitly lists come what may.

answered Jul 29 '11 at 07:51

Penfold

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You may want to complete the picture here by showing what happens when `f1` defines the prototype. – Zaid Jul 29 '11 at 08:05
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Re "Why?", in what context do you think a list of arguments should be constructed? – ikegami Jul 29 '11 at 08:30

How does func2 know the context?

2 Answers2