Please explain "and next"

[Dave Saville]

Came across this today

print "1 OK\n" and next unless (length $line[0]);

Never seen that construct before. Is it just some perlish shorthand
to get stuff on one line?

TIA

 

[Peter J. Holzer]

Came across this today

print "1 OK\n" and next unless (length $line[0]);

Never seen that construct before. Is it just some perlish shorthand
to get stuff on one line?

See perldoc perlop "Logical And" and perldoc -f next.
You should be able to figure it out.

hp

 

[Rainer Weikusat]

Came across this today

print "1 OK\n" and next unless (length $line[0]);

Never seen that construct before. Is it just some perlish shorthand
to get stuff on one line?

In this case, it's just a verbose and somewhat byzantine way to express

print("1 OK\n), next unless length($line[0]);

Generally, the so-called 'logical operators', (||, &&, //, and, or)
don't evaluate their right-hand arguments if the value of the combined
expression is already known after evaluating the left-hand
argument. This implies they can be used for flow-control in the sense
that code making up the right-hand argument will only be executed when
executeing the code of the left-hand argument wasn't sufficient to
determine the result of the expression. The line you quoted is a bad
example because the 'next' isn't really executed conditionally because
the print-statement always returns true. A better example could be
something like

$age >= 18 or die("Won't sell this to you.");

 

[Bjoern Hoehrmann]

* Rainer Weikusat wrote in comp.lang.perl.misc:

Came across this today

print "1 OK\n" and next unless (length $line[0]);

Never seen that construct before. Is it just some perlish shorthand
to get stuff on one line?

In this case, it's just a verbose and somewhat byzantine way to express

print("1 OK\n), next unless length($line[0]);

The line you quoted is a bad example because the 'next' isn't really
executed conditionally because the print-statement always returns true.
A better example could be something like

$age >= 18 or die("Won't sell this to you.");

Actually, `print` returns a true value only if successful and it might
have failed for any number of reasons, like a closed socket, a full hard
disk, and other IO problems like that.

 

[Rainer Weikusat]

* Rainer Weikusat wrote in comp.lang.perl.misc:

Came across this today

print "1 OK\n" and next unless (length $line[0]);

Never seen that construct before. Is it just some perlish shorthand
to get stuff on one line?

In this case, it's just a verbose and somewhat byzantine way to express

print("1 OK\n), next unless length($line[0]);

The line you quoted is a bad example because the 'next' isn't really
executed conditionally because the print-statement always returns true.
A better example could be something like

$age >= 18 or die("Won't sell this to you.");

Actually, `print` returns a true value only if successful and it might
have failed for any number of reasons, like a closed socket, a full hard
disk, and other IO problems like that.

But that's exceedingly unlikely because print just copies the output
data into an internal buffer and I doubt that the intention behind the
original code was to continue execution when print failed.

 

[George Mpouras]

Στις 19/1/2014 17:02, ο/η Dave Saville έγÏαψε:

print "1 OK\n" and next unless (length $line[0]);

use strict;
use warnings;

while (<DATA>) {
chomp;
my @line = split /,/;
print "1 OK\n" and next unless (length $line[0]);
print "id $line[1]\n";
}

__DATA__
,id00
aaaaaaaaaa,id01
bbbbbbbbb,id02
cccccccc,id03
,id04
,id05