perl function with otpional parameters

[donny750]

hi,

It's possible to create a perl function with optional parameter ?
For example,
i can call my function like this
test(param1) or test(param1,optionalparam)


Thanks

 

[Mike042]

Yes it is. Obviously in the function you will need to test for one, two or more parameters passed. Perl is very 'relaxed' about this sort of thing. Don't pass enough parameters and Perl says it will assume 'null' or 'empty string'. Pass too many parameters and Perl ignores the excess.

I hope that helps.

Mike

 

[MikeLacey]

Hi,

You declare the function first of all using a prototype, telling Perl how the function will be called. Like this.

sub myfunction ($$$;$);

This tells Perl that later on in your script you will be defining a function called myfunction which must be called with at least 3 scalars in the parameter list and may have 4.

and like this.

sub my2ndfunction ($%);

This tells Perl that later on in your script you will be defining a function called my2ndfunction which must be called with one scalar and one hash in the parameter list.

A semicolon separates mandatory arguments from the optional. It isn't useful before a @ or %, as these take variable numbers of arguments themselves and will just "gobble up" any other parameters in the list.

More information in the Perl documentation in perlsub - look for the section on Prototypes.

Mike

The options are: fast, cheap and right - pick any two... &

Want great answers to your Tek-Tips questions? Have a look at faq219-2884

 

[donny750]

yes, i've see
thanks
if i pass any value for a parameter,
perl ignore him

 

[KevinADC]

donny750

Do you mean sub routine instead of function?

http://perldoc.perl.org/perlsub.html

- Kevin, perl coder unexceptional!

 

[donny750]

a sub or function is the same thing ?

my function is like this

sub cal {
my var1 = shift;
my var2 = shift;

...code...


}

 

[KevinADC]

In perl, the term subroutine and function can be used interchangeably. The difference is really between a prototype, which MikeLacey described above, and a function/subroutine.

I doubt you need to use a protoype, but maybe there is a reason.



- Kevin, perl coder unexceptional!

 

[stevexff]

Most people don't use prototypes, they just shift off the parameters and examine them inside the sub, applying defaults for any that are missing or die if they are mandatory.

Steve

[small]"Every program can be reduced by one instruction, and every program has at least one bug. Therefore, any program can be reduced to one instruction which doesn't work." (Object:erlDesignPatterns)[/small]

 

[Mike042]

Perl has a neat little construct to save all that 'shifting', as follows:

   sub cal {
   my ($var1, $var2) = @_;

   ... code ...
   }

I hope that helps.

Mike