About the + in front of a hashref that disambiguates from a code block.

PoorLuzer has asked for the wisdom of the Perl Monks concerning the following question:

Replies are listed 'Best First'.
Re: About the + in front of a hashref that disambiguates from a code block. by Anonymous Monk on Oct 24, 2009 at 11:00 UTC
Try grepping the logs at http://perl5.git.perl.org/perl.git :D	[reply]
Re: About the + in front of a hashref that disambiguates from a code block. by ikegami (Patriarch) on Oct 24, 2009 at 16:36 UTC
When was it first introduced? I wonder if unary-plus existed before this use came about. If so, I wonder if it ever numified. How did people go around the issue before this was introduced? The ambiguity problem usually come from omitting parens around function calls. The solution is just to add the parens. `map +(3+$_)4, ... === map( (3+$_)4, ... )` [download]	[reply] [d/l]
Re^2: About the + in front of a hashref that disambiguates from a code block. (unary -) by tye (Sage) on Oct 24, 2009 at 18:58 UTC
I'm pretty sure unary plus existed very early in Perl (it makes perfect sense for it to have been included in the first version of the expression grammar). Not only did early unary + not numerify, I verified that in Perl 4 unary + didn't even impose scalar context. Now, unary minus actually did numerify in Perl 4. It was early in Perl 5 when unary minus was taught to just prepend '-' when applied to a string. And I think there was a slight delay between that and `-(-bar)` being taught to yeild '+bar'. There was also some early finagling to make `-bar => ...` not complain about 'bareword' even under 'use strict;'. - tye	[reply] [d/l] [select]
Re^3: About the + in front of a hashref that disambiguates from a code block. (unary -) by JavaFan (Canon) on Oct 24, 2009 at 22:39 UTC
Not only did early unary + not numerify Late unary + doesn't numerify either: $ perl -wE 'say +"foo"' foo $ [download]	[reply] [d/l]
Re^4: About the + in front of a hashref that disambiguates from a code block. (unary -) by ikegami (Patriarch) on Oct 24, 2009 at 23:03 UTC
Re^2: About the + in front of a hashref that disambiguates from a code block. by JavaFan (Canon) on Oct 24, 2009 at 16:39 UTC
I wonder if unary-plus existed before this use came about. I'm pretty sure unary plus has been around since perl 1.0.0. I seriously doubt that writing '+1' in perl 1.0.0 resulted in an error. In fact, I've a hard time thinking of a programming language that doesn't have unary plus.	[reply]


laziness, impatience, and hubris
	PerlMonks