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Re: constants wont optimize

by Somni (Friar)
on Jul 10, 2011 at 00:13 UTC ( #913560=note: print w/replies, xml ) Need Help??

in reply to constants wont optimize

Ah, Juerd's comment about return explains why I was unable to replicate your problem with any version of perl I have. I automatically corrected it when writing my test code.

Anyways, in case someone is interested, here's the test code. I've modified it to show the problem with return; it won't work on Windows as is, you'll have to remove the 2>/dev/null.

#!/usr/bin/perl -w use strict; { my $const_return = 'BEGIN { eval "sub HAS () { return 1 }" }'; my $const_noreturn = 'BEGIN { eval "sub HAS () { 1 }" }'; my $const_use = 'use constant; BEGIN { constant->import( HAS +=> 1 ) }'; my $paren = 'print HAS;'; my $noparen = 'print HAS();'; print( 'return, with parens ', run($const_return, $paren ), +"\n", 'return, without parens ', run($const_return, $noparen), +"\n", 'noreturn, with parens ', run($const_noreturn, $paren ), +"\n", 'noreturn, without parens ', run($const_noreturn, $noparen), +"\n", 'use, with parens ', run($const_use, $paren ), +"\n", 'use, without parens ', run($const_use, $noparen), +"\n", ); } sub run { my($code) = join ' ', @_; my @normal = qx{perl -wle \Q$code\E }; my @deparse = qx{perl -MO=Deparse -wle \Q$code\E 2>/dev/null}; chomp(my $normal_output = $normal[-1]); chomp(my $deparse_output = $deparse[-1]); return join ' ', $normal_output, $deparse_output; }

And some example output, with 5.12.2:

> px 5.12.2 ./ return, with parens 1 print HAS; return, without parens 1 print HAS; noreturn, with parens 1 print 1; noreturn, without parens 1 print 1; use, with parens 1 print 1; use, without parens 1 print 1;

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Re^2: constants wont optimize
by Marshall (Canon) on Jul 10, 2011 at 04:20 UTC
    on Windows as is, you'll have to remove the 2>/dev/null

    On Windows the equivalent of the Unix /dev/null device, the "bit bucket", is the "file" called NUL. Note one 'L'. 2>NUL is same as 2>/dev/null on Unix.

    The case of the name NUL can be anything, nUl, etc. This name is reserved by Windows in all directories - you cannot make a file called NUL. ">type NUL" prints nothing instead of printing "file not found".

      $ perl -MFile::Spec -le " print File::Spec->devnull" nul
      perlport - Writing portable Perl

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