Re: Reverse If and Normal Else
On Sep 22, Frank Geueke, III said:
display_nothing() if ($match_type eq 'none');
else
{
}
Now I like the reverse if because it takes up one line
instead of four (I like braces on their own lines -
see else). But this error...
syntax error at
/usr2/login/fjg/hotspot_tracker/search_by_ip_or_mac.cgi
line 70, near else
...keeps coming up. Is there a way to keep the
reverse if and use an else (or something like it) that
anyone knows of? Thanks. ~Frank
No, there isn't. Not with 'else', at least. You could use a ternary
(hook) operator:
($match_type eq 'none') ?
display_nothing() :
display_something();
is like saying
if ($match_type eq 'none') {
display_nothing();
}
else {
display_something();
}
--
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Re: Reverse If and Normal Else
Frank Geueke, III wrote:
Hi everyone.
Okay, so maybe this one is a silly question. I have a
fairly large script and I have a bunch of places where
I'm following a reverse if with a normal else and perl
keeps complaining about it. It seems to make sense to
me, but I guess its bad syntax. Here is one of them:
display_nothing() if ($match_type eq 'none');
else
{
}
Now I like the reverse if because it takes up one line
instead of four (I like braces on their own lines -
see else). But this error...
Not really because the ; is a statement terminator. If it is really
about the number of lines there is nothing preventing you from just
putting it all on one line.
if ($match_type eq 'none') { display_nothing(); }
else
{
}
Personally I would rather see it just written out, a couple lines make
little difference if the rest of your code is structured well.
I suppose you could also reverse the logic and then your display_nothing
would get shoved to the bottom of the whole block which is typically
what I would do, so,
if ($match_type ne 'none')
{
}
else { display_nothing(); }
Or,
unless ($match_type eq 'none')
{
}
else { display_nothing(); }
HTH,
http://danconia.org
syntax error at
/usr2/login/fjg/hotspot_tracker/search_by_ip_or_mac.cgi
line 70, near else
...keeps coming up. Is there a way to keep the
reverse if and use an else (or something like it) that
anyone knows of? Thanks. ~Frank
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Re: Reverse If and Normal Else
Frank Geueke, III wrote:
Hi everyone.
Hello,
Okay, so maybe this one is a silly question. I have a
fairly large script and I have a bunch of places where
I'm following a reverse if with a normal else and perl
keeps complaining about it. It seems to make sense to
me, but I guess its bad syntax. Here is one of them:
display_nothing() if ($match_type eq 'none');
else
{
}
Now I like the reverse if because it takes up one line
instead of four (I like braces on their own lines -
see else). But this error...
syntax error at
/usr2/login/fjg/hotspot_tracker/search_by_ip_or_mac.cgi
line 70, near else
...keeps coming up. Is there a way to keep the
reverse if and use an else (or something like it) that
anyone knows of?
The if statement modifier is just another way to write a logical and statement:
$ perl -MO=Deparse -e' display_nothing() if $match_type eq q/none/ '
display_nothing() if $match_type eq 'none';
-e syntax OK
$ perl -MO=Deparse -e' $match_type eq q/none/ and display_nothing() '
display_nothing() if $match_type eq 'none';
-e syntax OK
$ perl -MO=Deparse -e' $match_type eq q/none/ display_nothing() '
display_nothing() if $match_type eq 'none';
-e syntax OK
John
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Re: Reverse If and Normal Else
On Sep 22, John W. Krahn said:
The if statement modifier is just another way to write a logical and statement:
$ perl -MO=Deparse -e' display_nothing() if $match_type eq q/none/ '
display_nothing() if $match_type eq 'none';
-e syntax OK
$ perl -MO=Deparse -e' $match_type eq q/none/ and display_nothing() '
display_nothing() if $match_type eq 'none';
-e syntax OK
$ perl -MO=Deparse -e' $match_type eq q/none/ display_nothing() '
display_nothing() if $match_type eq 'none';
-e syntax OK
An important difference, though, is that the if statement modifier takes
an expression and produces a statement, so you can't store its return
value somewhere. That is,
$result = (do_this() if that());
is a syntax error. Not so in the case of '' and 'and':
$result = (that() and do_this());
$result = (that() do_this());
However, you can turn any statement into an expression by using do { }
around the statement:
$result = do { do_this() if that(); };
--
Jeff japhy Pinyan% How can we ever be the sold short or
RPI Acacia Brother #734% the cheated, we who for every service
http://www.perlmonks.org/ % have long ago been overpaid?
http://princeton.pm.org/ %-- Meister Eckhart
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