Trivial 'unless' Question

[Steve Grazzini]

On Tue, Oct 21, 2003 at 12:17:17PM -0700, Jeff Westman wrote:

> # ... but can I do something like....
> print "first\n" unless ($counter) else { print "second\n";

Not really. You could use the conditional operator, though.

print $counter ? "second\n" : "first\n";

--
Steve

[Jeff Westman]

Hi ..... very trivial ... is there a way or correct syntax to add an 'if' tp
the following 'unless' statement?

# this works fine ...
print "first\n" unless ($counter);
# ... but can I do something like....
print "first\n" unless ($counter) else { print "second\n";
# (syntax error)

I know I can do this:

#!/usr/bin/perl
use warnings;
use strict;
my $counter = 0;

unless ($counter) {
print "first\n";
} else {
print "second\n";
}

..... but I wanted to put the 'unless' later in the statement. I couldn't
find anything in the FAQ or perldoc on this one.

TIA!

-JW




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[Steve Grazzini]

On Tue, Oct 21, 2003 at 01:06:44PM -0700, Jeff Westman wrote:

> Steve Grazzini <grazz@pobox.com> wrote:

> > On Tue, Oct 21, 2003 at 12:17:17PM -0700, Jeff Westman wrote:

> > > # ... but can I do something like....
> > > print "first\n" unless ($counter) else { print "second\n";

> >
> > Not really. You could use the conditional operator, though.
> >
> > print $counter ? "second\n" : "first\n";

>
> True, but I was looking for a way to do this with a somewhat "buried"
> unless keyword.

print +( qw(second first --> unless <--) )[ not $counter ];

--
Steve

[Jeff Westman]

Steve Grazzini <grazz@pobox.com> wrote:

> On Tue, Oct 21, 2003 at 12:17:17PM -0700, Jeff Westman wrote:

> > # ... but can I do something like....
> > print "first\n" unless ($counter) else { print "second\n";

>
> Not really. You could use the conditional operator, though.
>
> print $counter ? "second\n" : "first\n";

True, but I was looking for a way to do this with a somewhat "buried" unless
keyword.

TA

-JW

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The New Yahoo! Shopping - with improved product search
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[Kevin Pfeiffer]

In article <20031021195420.GE10120@grazzini.net>, Steve Grazzini wrote:

> On Tue, Oct 21, 2003 at 01:06:44PM -0700, Jeff Westman wrote:

>> Steve Grazzini <grazz@pobox.com> wrote:

>> > On Tue, Oct 21, 2003 at 12:17:17PM -0700, Jeff Westman wrote:
>> > > # ... but can I do something like....
>> > > print "first\n" unless ($counter) else { print "second\n";
>> >
>> > Not really. You could use the conditional operator, though.
>> >
>> > print $counter ? "second\n" : "first\n";

>>
>> True, but I was looking for a way to do this with a somewhat "buried"
>> unless keyword.

>
> print +( qw(second first --> unless <--) )[ not $counter ];

??? :-|


--
Kevin Pfeiffer

[Alan Perry]

On Tuesday, October 21, 2003 16:01, Kevin Pfeiffer wrote:

>In article <20031021195420.GE10120@grazzini.net>, Steve Grazzini wrote:
>

>> On Tue, Oct 21, 2003 at 01:06:44PM -0700, Jeff Westman wrote:

>>> Steve Grazzini <grazz@pobox.com> wrote:
>>> > On Tue, Oct 21, 2003 at 12:17:17PM -0700, Jeff Westman wrote:
>>> > > # ... but can I do something like....
>>> > > print "first\n" unless ($counter) else { print "second\n";
>>> >
>>> > Not really. You could use the conditional operator, though.
>>> >
>>> > print $counter ? "second\n" : "first\n";
>>>
>>> True, but I was looking for a way to do this with a somewhat "buried"
>>> unless keyword.

>>
>> print +( qw(second first --> unless <--) )[ not $counter ];

>
>??? :-|
>

I think the author was trying to be cute... I got a chuckle out of it!

print +( qw(second first --> unless <--) )[ not $counter ];

Basically, you are creating an anonymous (right term?) array, and printing
the "not $counter"'th element. So if $counter is 0, you print "first",
otherwise you print "second". The other stuff in the array is there just to
satisfy the "buried" unless requested by the OP. However, as you see here,
it does not use the keyword "unless", just a string "unless". The only
elements that will ever be accessed are "second" and "first"...

It could also be written as:

print +( qw(second first) )[ not $counter ];

HTH
Alan

[Roy Johnson]

[email]westfour@yahoo.com[/email] (Jeff Westman) wrote in message news:<20031021191717.66026.qmail@web41107.mail.yah oo.com>...

> # ... but can I do something like....
> print "first\n" unless ($counter) else { print "second\n";

The predicate conditionals are limited: there is no elsing with them.
The suggestion to use the ternary operator (?:) is appropriate for
this example. If you really wanted to sneak some more conditional
logic into a predicate, you'll have to do it with operators:
print "first\n" unless ($counter and print "second\n");

I strongly advise against that sort of garbling. It would be much
clearer to write
print(($counter) ? 'second'
: 'first'
, "\n");
or just
if ($counter == 0) { print "first\n" }
else { print "second\n" }