«

I know you can do this, I just can't find it.
How do you call a sub within a qq{} construct

qq{The common term for H2O is chem("H2O").}

Thank you

(As soon is this post is complete... I'll find it)

cate wrote:
> I know you can do this, I just can't find it.
> How do you call a sub within a qq{} construct
>
> qq{The common term for H2O is chem("H2O").}

perldoc -q "How do I expand function calls in a string"



John
--
The programmer is fighting against the two most
destructive forces in the universe: entropy and
human stupidity. -- Damian Conway

On Feb 2, 10:18*am, "John W. Krahn" <some...@example.com> wrote:
> cate wrote:
> > I know you can do this, I just can't find it.
> > How do you call a sub within a qq{} construct
>
> > qq{The common term for H2O is chem("H2O").}
>
> perldoc -q "How do I expand function calls in a string"
>
> John
> --
> The programmer is fighting against the two most
> destructive forces in the universe: entropy and
> human stupidity. * * * * * * * -- Damian Conway

@{[mysub(1,2,3)]}
good grief. Thanks

>>>>> "c" == cate <> writes:

c> On Feb 2, 10:18*am, "John W. Krahn" <some...@example.com> wrote:
>> cate wrote:
>> > I know you can do this, I just can't find it.
>> > How do you call a sub within a qq{} construct
>>
>> > qq{The common term for H2O is chem("H2O").}
>>
>> perldoc -q "How do I expand function calls in a string"
>>
c> @{[mysub(1,2,3)]}
c> good grief. Thanks

and that is considered a poor construct. i never use it (or its scalar
cousin) nor do i recommend it. when i review code, i downgrade when i
see that used. it is simpler and better to just assign to a variable
before the string and then interpolate it. also it will likely be faster
as you don't need the reference/dereference. also it will only call your
code in a list context (even the scalar form!) which may be a
problem. assigning to your own variable allows you to control the
context as well.

uri

--
Uri Guttman ------ -------- http://www.sysarch.com --
----- Perl Code Review , Architecture, Development, Training, Support ------
--------- Gourmet Hot Cocoa Mix ---- http://bestfriendscocoa.com ---------

cate <> writes:

> I know you can do this, I just can't find it.
> How do you call a sub within a qq{} construct
>
> qq{The common term for H2O is chem("H2O").}
>
> Thank you
>
> (As soon is this post is complete... I'll find it)

perl -e '
sub chem {
my $term = shift;
return "*$term*";
}
print qq{The common term for H2O is ${\( chem("H2O") ) }};
'

use @{...} for list expressions, ${...} for scalar.

See perldoc perlref section Using References, item 4.

--
John Bokma j3b

Hacking & Hiking in Mexico - http://johnbokma.com/
http://castleamber.com/ - Perl & Python Development

>>>>> "JB" == John Bokma <> writes:

JB> cate <> writes:
>> I know you can do this, I just can't find it.
>> How do you call a sub within a qq{} construct
>>
>> qq{The common term for H2O is chem("H2O").}
>>
>> Thank you
>>
>> (As soon is this post is complete... I'll find it)

JB> perl -e '
JB> sub chem {
JB> my $term = shift;
JB> return "*$term*";
JB> }
JB> print qq{The common term for H2O is ${\( chem("H2O") ) }};
JB> '

JB> use @{...} for list expressions, ${...} for scalar.

partly incorrect.

perl -le 'sub context {return "array" if wantarray} ; print "scalar ${\context()}"'
scalar array

that is an obscure bug that has been around a long time. the scalar form
still calls the sub in list context. this is one of the reasons i don't
recommend using this trick. and a trick it is. it isn't really meant to
be used like that but perl's syntax supports interpolating of
dereferenced expressions. the interpolate module supports this in a
better way and so does perl6.

uri

--
Uri Guttman ------ -------- http://www.sysarch.com --
----- Perl Code Review , Architecture, Development, Training, Support ------
--------- Gourmet Hot Cocoa Mix ---- http://bestfriendscocoa.com ---------

>>>>> "BM" == Ben Morrow <> writes:

BM> Quoth "Uri Guttman" <>:
>> >>>>> "JB" == John Bokma <> writes:
>>
JB> cate <> writes:
>> >> I know you can do this, I just can't find it.
>> >> How do you call a sub within a qq{} construct
>> >>
>> >> qq{The common term for H2O is chem("H2O").}
>> >>
>> >> Thank you
>> >>
>> >> (As soon is this post is complete... I'll find it)
>>
JB> perl -e '
JB> sub chem {
JB> my $term = shift;
JB> return "*$term*";
JB> }
JB> print qq{The common term for H2O is ${\( chem("H2O") ) }};
JB> '
>>
JB> use @{...} for list expressions, ${...} for scalar.
>>
>> partly incorrect.
>>
>> perl -le 'sub context {return "array" if wantarray} ; print "scalar
>> ${\context()}"'
>> scalar array
>>
>> that is an obscure bug that has been around a long time. the scalar form
>> still calls the sub in list context.

BM> It's not a bug. \($x, $y, $z) is perfectly valid, and returns a list of
BM> refs. (This also means that \(@a) is not the same as \@a: one of the few
BM> cases where parens *are* necessary to denote a list.)

yes, but the "${\foo()}" idiom looks like it will be in scalar
context. that is the issue. you need to put a scalar() in there. whether
it is a true bug or not, i say this is one reason to not use this
trick. using a variable is simpler, probably faster and safer.

uri

--
Uri Guttman ------ -------- http://www.sysarch.com --
----- Perl Code Review , Architecture, Development, Training, Support ------
--------- Gourmet Hot Cocoa Mix ---- http://bestfriendscocoa.com ---------

>>>>> "BM" == Ben Morrow <> writes:

BM> Quoth "Uri Guttman" <>:
>> >>>>> "BM" == Ben Morrow <> writes:
>>
BM> It's not a bug. \($x, $y, $z) is perfectly valid, and returns a list of
BM> refs. (This also means that \(@a) is not the same as \@a: one of the few
BM> cases where parens *are* necessary to denote a list.)
>>
>> yes, but the "${\foo()}" idiom looks like it will be in scalar
>> context. that is the issue. you need to put a scalar() in there. whether
>> it is a true bug or not, i say this is one reason to not use this
>> trick. using a variable is simpler, probably faster and safer.

BM> Oh, I agree there. The right answer is of course some sort of template
BM> system: sprintf will do for starters, and there are plenty on CPAN.

and what is wrong with my suggestio of a simple variable assignment
before the string is built? that is all the OP needs.

uri

--
Uri Guttman ------ -------- http://www.sysarch.com --
----- Perl Code Review , Architecture, Development, Training, Support ------
--------- Gourmet Hot Cocoa Mix ---- http://bestfriendscocoa.com ---------

"Uri Guttman" <> writes:

>>>>>> "JB" == John Bokma <> writes:
>
> JB> cate <> writes:
> >> I know you can do this, I just can't find it.
> >> How do you call a sub within a qq{} construct
> >>
> >> qq{The common term for H2O is chem("H2O").}
> >>
> >> Thank you
> >>
> >> (As soon is this post is complete... I'll find it)
>
> JB> perl -e '
> JB> sub chem {
> JB> my $term = shift;
> JB> return "*$term*";
> JB> }
> JB> print qq{The common term for H2O is ${\( chem("H2O") ) }};
> JB> '
>
> JB> use @{...} for list expressions, ${...} for scalar.
>
> partly incorrect.

I stand corrected, thanks (Ben too). I haven't used this construct for
ages, don't really like it.

--
John Bokma j3b

Hacking & Hiking in Mexico - http://johnbokma.com/
http://castleamber.com/ - Perl & Python Development

with <> Uri Guttman wrote:
*SKIP*
> yes, but the "${\foo()}" idiom looks like it will be in scalar
> context. that is the issue. you need to put a scalar() in there. whether
> it is a true bug or not, i say this is one reason to not use this
> trick. using a variable is simpler, probably faster and safer.

s/probably/definetely/

#!/usr/bin/perl

use strict;
use warnings;
use Benchmark qw{ cmpthese timethese };

sub abc {
return "abc";
}
sub def {
my $t = "def";
return "*$t";
}
my( $x, $y );

cmpthese timethese -5, {
code00 => sub { $x = "@{[ abc ]}"; },
code01 => sub { $x = "${\( def )}"; },
code02 => sub { $y = abc; $x = "$y"; },
};

__END__
Benchmark: running code00, code01, code02 for at least 5 CPU seconds...
code00: 6 wallclock secs ( 5.17 usr + 0.00 sys = 5.17 CPU) @ 559916.63/s (n=2894769)
code01: 7 wallclock secs ( 5.09 usr + 0.00 sys = 5.09 CPU) @ 667528.49/s (n=3397720)
code02: 7 wallclock secs ( 5.27 usr + 0.00 sys = 5.27 CPU) @ 941641.56/s (n=4962451)
Rate code00 code01 code02
code00 559917/s -- -16% -41%
code01 667528/s 19% -- -29%
code02 941642/s 68% 41% --

p.s. "faster" is strawman, anyway


--
Torvalds' goal for Linux is very simple: World Domination
Stallman's goal for GNU is even simpler: Freedom