Re: Mr. Ternary is greater than Mrs. If Else

Don't you dare to sow strife between Mrs. If Else and Mr. Ternary!

They've lived together a couple of years now, and I will not let you induce quarrel amongst them over 'who is greater'!

Both serve different purposes. Mrs. If Else provides for blocks of code to be executed conditionally, whereas Mr. Ternary shortcuts them with a single statement (if they resolve to simple expressions) or delegates them elsewhere (probably to Mrs. If Else again, appearing in some sub).

They often interchange tasks, as most mordern couples do; but mostly Mr. Ternary likes to prepare hesh bugs while Mrs. If Else studies blocks of stock exchange charts to see what's best.

I'd rewrite your Mr. Ternary code like this

#!perl/bin/perl

use strict;

print "Are you sure you want to quit ('yes' or any key for 'no'): ";
chomp($_ = <STDIN>);

print /\byes\b/i ? <<LEAVE : <<STAY;

Press any key to exit...
LEAVE
Thanks, you stayed... But then, goodbye.
Press any key to proceed...
STAY
<STDIN>;
print "GOOD DAY\n";
[download]

to better show where Mr. Ternary shines - inlining a decision.

Now, to your delimma (++ alone for mispelling dilemma twice in one post :-):

In the expression

$foo = 1; $foo ? \& { print "foo"} : \& { print "bar"};
[download]

The ampersand & marks the following { } construct as a code block; the backslash disambiguates that operation from binary '&' (the bitwise AND) and returns a reference for that code block. Last, Mr. Ternary happily evaluates those references based on the 'truthness' of $foo. This is, at least, my interpretation of things, but I might be wrong. I never used that construct before...

update And I am wrong! See betterworld's comment below.

Nice post!

--shmem

_($_=" "x(1<<5)."?\n".q·/)Oo.  G°\        /
                              /\_¯/(q    /
----------------------------  \__(m.====·.(_("always off the crowd"))."·
");sub _{s./.($e="'Itrs `mnsgdq Gdbj O`qkdq")=~y/"-y/#-z/;$e.e && print}

Comment on Re: Mr. Ternary is greater than Mrs. If Else Select or Download Code

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Re^2: Mr. Ternary is greater than Mrs. If Else by betterworld (Curate) on May 20, 2007 at 01:11 UTC
The ampersand & marks the following { } construct as a code block; the backslash disambiguates that operation from binary '&' (the bitwise AND) and returns a reference for that code block. It's not really a code block. `\&{foo}` is a reference to the subroutine with the name "foo". Similarly, `\& { print "foo" }` is a reference to the subroutine with the name that is returned by print, i. e. it's `\&1` (unless print fails). `$ perl -lwe 'my $code = \&{print "foo"}' foo $ perl -lwe 'my $code = \&{print "foo"}; $code->()' foo Undefined subroutine &main::1 called at -e line 1.` [download] (Note that `$code` is not called/dereferenced in the first one-liner, yet it prints foo.	[reply] [d/l] [select]
Re^3: Mr. Ternary is greater than Mrs. If Else by blazar (Canon) on May 20, 2007 at 14:03 UTC
It's not really a code block. `\&{foo}` is a reference to the subroutine with the name "foo". Similarly, `\& { print "foo" }` is a reference to the subroutine with the name that is returned by print, i. e. it's `\&1` (unless print fails). Well, there's a subtle difference. When you write `&{foo}` -with no quotes within the curlies-, that's (almost) just as if you had written `&foo`. This is not specific of subs, but of quite about all kind of variables: `spock:~ [16:02:30]$ perl -wMstrict -le 'my $x=1; print ${x}' Ambiguous use of ${x} resolved to $x at -e line 1. 1 spock:~ [16:02:36]$ perl -wMstrict -le 'my $x=1; print ${"x"}' Can't use string ("x") as a SCALAR ref while "strict refs" in use at - +e line 1.` [download]	[reply] [d/l] [select]