Concatenation: $i.$j different from "$i$j"

[Occidental]

{
my $i = "TT";
my $j = "AT";

if ("$i$j" =~ /X/)
{
print "$i$j matched\n";
}
else
{
print "$i$j not matched\n";
}
}

{
my $i = "TT";
my $j = "AT";

if ($i.$j =~ /X/)
{
print $i.$j . " matched\n";
}
else
{
print $i.$j . " not matched\n";
}
}

gives

TTAT not matched
TTAT matched

Can anyone explain?

 

[xhoster]

if ($i.$j =~ /X/)

Can anyone explain?

Precedence can. =~ is two lines above . in the perlop list of
precedences.

$ perl -MO=Deparse,-p -e ' "x"."y" =~ /f/'
('x' . ('y' =~ /f/));
-e syntax OK

Xho

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this fact.

 

[John W. Krahn]

{
my $i = "TT";
my $j = "AT";

if ("$i$j" =~ /X/)
{
print "$i$j matched\n";
}
else
{
print "$i$j not matched\n";
}
}

{
my $i = "TT";
my $j = "AT";

if ($i.$j =~ /X/)
{
print $i.$j . " matched\n";
}
else
{
print $i.$j . " not matched\n";
}
}

gives

TTAT not matched
TTAT matched

Can anyone explain?

Yes, perl can:

$ perl -MO=Deparse,-p -e'
{
my $i = "TT";
my $j = "AT";

if ("$i$j" =~ /X/)
{
print "$i$j matched\n";
}
else
{
print "$i$j not matched\n";
}
}

{
my $i = "TT";
my $j = "AT";

if ($i.$j =~ /X/)
{
print $i.$j . " matched\n";
}
else
{
print $i.$j . " not matched\n";
}
}
'
{
(my $i = 'TT');
(my $j = 'AT');
if (("$i$j" =~ /X/)) {
print("$i$j matched\n");
}
else {
print("$i$j not matched\n");
}
}
{
(my $i = 'TT');
(my $j = 'AT');
if (($i . ($j =~ /X/))) {
print((($i . $j) . " matched\n"));
}
else {
print((($i . $j) . " not matched\n"));
}
}
-e syntax OK


if (("$i$j" =~ /X/)) {

Is false because there is no 'X' in 'TTAT'.

if (($i . ($j =~ /X/))) {

Is true because the string from the expression ($i . ($j =~ /X/)) is true.



John

 

[Dr.Ruud]

Occidental schreef:

if ("$i$j" =~ /X/)
if ($i.$j =~ /X/)

I heard somewhere that the next version of Python will make

1+2 * 3

behave differently from

1 + 2*3

 

[Dr.Ruud]

Abigail schreef:

Dr.Ruud:

If you had written 'Perl6' instead of 'Python', I would have assumed
you were serieus.

Hey, I was just aiming for a bigger publiek.