Perl Function Problem

premshree · 09-21-2002, 08:00 AM

Hello,

I am using the following code to test for operators :

Code:

sub isOperator
{
	($who)=@_;
	if($who=="+" || $who=="-"|| $who=="*" || $who=="/" || $who=="^")
	{
		return(true);
	}
	else
	{
		return(false);
	}
}

$get=<STDIN>;
if(isOperator($get))
{
	print $get;
}

The code should return true only when I enter '+', '-', '*', '/' or '^' but the code returns true for anything that I enter.

I can't figure out what is wrong. Please help!

FlashCoder · 09-21-2002, 09:03 AM

Try instead "==" will write "eq".
Ok?

premshree · 09-21-2002, 06:18 PM

You mean instead of using '==' to use 'eq' ?

Mouldy_Goat · 09-21-2002, 07:51 PM

Yes, use 'eq' instead of '=='. The former does a string comparison, whilst the second does a numerical comparison, which isn't what you want here.

Two other points worth noting:

Firstly, in your function you're writing return (true);. What this will actually do is return the string 'true', and so whilst it will evaluate to true in a boolean context - it means that return (false); will also return true.

Perl doesn't have any boolean 'true' or 'false'. Instead just use a '1' and a '0' to get the same effect - it's less typing anyway.

Also you're forgetting to chomp() $get. This means getting rid of the newline (if any) on the end of the variable, which will cause all of your equality tests in the isOperator() function to return false, because "+\n" is not the same as "+". (The \n stands for newline).

So your script should probably look something like this:

Code:

sub isOperator
{
	($who) = @_;
	if($who eq "+" || $who eq "-" || $who eq "*" || $who eq "/" || $who eq "^")
	{
		return 1;
	}
	else
	{
# because nothing is being returned, this will evaluate to false
		return;
	}
}

$get = <STDIN>;
chomp $get;
if(isOperator($get))
{
	print $get;
}

Hope that helps a bit.

premshree · 09-22-2002, 03:33 PM

Yea that worked! Thanks.

FlashCoder · 09-22-2002, 08:08 PM

Quote:

Originally posted by premshree
Yea that worked! Thanks.

premshree · 09-23-2002, 09:50 AM

I have a file print.pl

Code:

print '<html><head><title>Welcome</title></head><body>';
print param('exp');
print '</body></html>';

I run the file in the browser with URL as
http://localhost/cgi-bin/print.pl?exp=Premshree but the parameter 'exp' is not printed.

FlashCoder · 09-23-2002, 05:47 PM

Quote:

Originally posted by premshree
I have a file print.pl

Code:

print '<html><head><title>Welcome</title></head><body>'; print param('exp'); print '</body></html>';

I run the file in the browser with URL as
http://localhost/cgi-bin/print.pl?exp=Premshree but the parameter 'exp' is not printed.

code:

print $ENV{CONTENT_LENGTH};

Please, for more information e-mail me (bdenis@list.ru) and I ask to your question!!!

premshree · 09-24-2002, 03:05 PM

I am just trying to pass a parameter to a Perl file and print it on the browser. I don't want to use any CGI modules.

FlashCoder · 09-24-2002, 06:30 PM

Quote:

Originally posted by premshree
I am just trying to pass a parameter to a Perl file and print it on the browser. I don't want to use any CGI modules.

Sorry:

print $ENV{QUERY_STRING};

It write your parametr. It worked?

FlashCoder · 09-24-2002, 06:32 PM

Quote:

Originally posted by FlashCoder

Sorry:

print $ENV{QUERY_STRING};

It write your parametr. It worked?

For more information, Please e-mail me the letter in address^
den86@hotbox.ru or bdenis@list.ru and a will ask on your all questions and problems !!!

premshree · 09-25-2002, 08:02 AM

Yes, that printed the query string that I passed. Maybe I'll try to manipulate the query string to get the name-value pair.

FlashCoder · 09-25-2002, 10:52 AM

Quote:

Originally posted by premshree
Yes, that printed the query string that I passed. Maybe I'll try to manipulate the query string to get the name-value pair.

code:
($a, $b)=split(/=/,$ENV{QUERY_STRING});

print "\$a is ";$a;

Did I help you?

premshree · 09-25-2002, 02:21 PM

I used this :

Code:

@string=split(/&/,$ENV{QUERY_STRING});
@exp=split(/=/,$string[0]);
$expression=$exp[1];
$expression =~ tr/+/ /;
$expression =~ s/%([a-fA-F0-9][a-fA-F0-9])/pack("C", hex($1))/eg;
$expression =~ s/<!--(.|\n)*-->//g;
@act=split(/=/,$string[1]);
$action=$act[1];

It works great!

Mouldy_Goat · 09-25-2002, 05:25 PM

Just out of interest why aren't you using the CGI.pm module?

It comes as standard with the Perl distribution so you shouldn't have to fiddle about with installing it.

All you should have to do is:

Code:

#!/usr/bin/perl
use CGI qw(:standard);
print header;
print '<html><head><title>Welcome</title></head><body>';
print param('exp');
print '</body></html>';