'while', 'foreach' not in perlfunc

[throop]

Brethren,

Trying to look online for exactly how while binds $_. Oddly enough, searching at perl.org in index-functions does not turn up documentation for while, nor for foreach. The other Perl iterative constructs, grep and map are there, though.

I realize that grep and map return values, where while and foreach don't. Still, seems like they should be documented in the same place. Or am I thinking about it wrong?

throop

[pc88mxer]

Because they are considered statements and not functions, while and foreach are documented in perldoc perlsyn.

while doesn't do any binding except when calling readline or glob (either by name or by using the <...> syntax):

while (<STDIN>) { ... }
while (readline(STDIN)) { ...}

are equivalent to: while (1) { last unless defined($_ = <STDIN>); ... 
+}

while (glob("*.c")) { ... }
while (<*.c>) { ... }

are equivalent to: my @list = glob("*.c"); for (@list) { ... };

[dragonchild]

while and foreach and syntax, not functions. grep and map are also, technically, syntax, but they behave like functions. while and foreach do not, so they aren't documented in the same place.

[duelafn]

Yeah, though it would be nice if perldoc -f word worked for any perl keyword.

[dragonchild]

perlbug still works, as does supplying patches to p5p.

[psini]

I don't understand your question. while and foreach are documented in perlsyn as they are statement modifiers.

Update: I of course meant compound statements

[Anonymous Monk]

perltoc - perl documentation table of contents

As i understand it, you're asking for perldoc -k while

[blazar]

Oddly enough, searching at perl.org in index-functions does not turn up documentation for while, nor for foreach. The other Perl iterative constructs, grep and map are there, though.

I personally believe it's not odd at all: it is to be expected, since map and grep are not simply "iterative constructs" but actual functions, whereas while and for are flow control statements or statement modifiers. I believe that in Perl 6 they will become (more akin to) real functions, but that's not the case as of now.

[moritz]

I believe that in Perl 6 they will become (more akin to) real functions, but that's not the case as of now.

They will never be quite like ordinary functions, because they violate the "no two terms in a row":

# while:
while $cond { $statements }
# ordinary funtion:
my_while $cond, { $statements };

# allowed in ordinary functions:
my_while $cond, █
# not allowed in builtin while:
while $cond █

while is parsed like this in STD.pm:

rule statement_control:while {\
    <sym>
    [ <?before '(' [[my]? '$'\w+ '=']? '<' '$'?\w+ '>' ')'>   #'
        <.panic: "This appears to be Perl 5 code"> ]?
    <EXPR>                             {*}                      #= exp
+r
    <pblock>                           {*}                      #= blo
+ck
    {*}
}

So it's still special-cased. (It would be even without the check for Perl 5 constructs)