Problem with parameters in subroutines

aatrox has asked for the wisdom of the Perl Monks concerning the following question:

Replies are listed 'Best First'.
Re: Problem with parameters in subroutines by choroba (Cardinal) on Jun 02, 2014 at 12:15 UTC
As written, you subroutine can be called without parameters. Note that `write` is not a good subroutine name, though, as write already has a meaning in Perl. On the other hand, you can write the subroutine in a way it expects a parameter: `sub mywrite { my $candidate = shift; print "$candidate->{firstname} $candidate->{surname}:$candidate->{ +id}\n"; }` [download] This still look wrong, though. What's the relation between $guest and $kandydatkonkursu? لսႽ† ᥲᥒ⚪⟊Ⴙᘓᖇ Ꮅᘓᖇ⎱ Ⴙᥲ𝇋ƙᘓᖇ	[reply] [d/l] [select]
Re^2: Problem with parameters in subroutines by aatrox (Initiate) on Jun 02, 2014 at 12:24 UTC
its the same it was my big fault i forgot to translate subroutine sorry :F	[reply]
Re^2: Problem with parameters in subroutines by aatrox (Initiate) on Jun 02, 2014 at 12:30 UTC
Yeah this works !! Thank you so much!	[reply]
Re: Problem with parameters in subroutines by smls (Friar) on Jun 02, 2014 at 12:32 UTC
Others have already answered your more immediate question, but from the way you asked, it looks like you may have a misconception about how subroutine parameters work in the first place. All that passing parameters to a subroutine call does, is to make those values available to the subroutine in the special `@_` array. It does not automatically make each parameter a variable inside the subroutine, and in fact it won't have any effect at all if the subroutine does not choose to look at the contents of `@_`. Often, "looking at the contents of `@_`" is done implicitly using calls to shift, hence the `my $candidate = shift;` in the above answer. If you need more explanation, please read perlintro#Writing-subroutines.	[reply] [d/l] [select]
Re^2: Problem with parameters in subroutines by aatrox (Initiate) on Jun 02, 2014 at 14:05 UTC
Ok thanks for explanation. Im already learning perl from yesterday and sometimes it looks strange for me :) I have got next question with loops: If i have got loop: `foreach $guest(@people) { if($guest->{'ident'} =~ /^1[014689]7[014689]5[014689]3[ +014689]2[014689]$/) { mywrite($guest); #my print function } }` [download] And i want change this foreach loop to for loop it should looks like that? `$arraylenght = lenght($guests); for($i = 0 ; i < $arraylenght ; $i++) { }` [download] Im thinking how i can change this loop foreach to for loop workinkg for this example im trying to do this to practise. I was reading abour foreach loop and i think here guests is a array of people and &guest are one person from this array. Is it maybe possible to do something like this? `$arraylenght = lenght($guests); for($i = 0 ; i < $arraylenght ; $i++) { if($guest->{'ident'} =~ /^1[014689]7[014689]5[014689]3[014689]2[01 +4689]$/) { mywrite($guest); #my print function } }` [download]	[reply] [d/l] [select]
Re^3: Problem with parameters in subroutines by smls (Friar) on Jun 02, 2014 at 14:30 UTC
This is how you would write it as a C-style for loop: `for (my $i=0; $i <= $#people; $i++) { if($people[$i]{'ident'} =~ /^1[014689]7[014689]5[014689]3[01468 +9]2[014689]$/) { mywrite($people[$i]); #my print function } }` [download] Comments: `@people` is an array, and `$people[$i]` is the element with index `$i` in that array. The `foreach` version of the loop automatically maps the current array element to a new variable (`$guest` in this case) which is nicer to type and read than `$people[$i]`, which is why that kind of loop is usually preferable. `$#people` is the correct syntax for referring to the last index of the `@people` array. The length function is only used to get the length of a string, not the number of elements in an array. In any case, I strongly recommend that you carefully read through the whole perlintro page (and especially the "Perl variable types" section); it will make learning Perl much easier than trying to figure out the basics by trial-and-error. After that, perlreftut makes for good further reading. --- Update: Fixed link; thanks taint!*	[reply] [d/l] [select]
Re^4: Problem with parameters in subroutines by taint (Chaplain) on Jun 02, 2014 at 14:46 UTC
Re: Problem with parameters in subroutines by LanX (Saint) on Jun 02, 2014 at 12:11 UTC
`sub write { my ($contestant) = @_; print "$contestant->{'nazwisko'} "; print "$contestant->{'imie'}"; print ":$contestant->{'id'}\n"; }` [download] it's hard to tell from the code giveną how to best call `write()` If your claims are right, this should work `write($kandydatkonkursu)` ... ...but I think it should rather be `write($guest)`! Cheers Rolf ( addicted to the Perl Programming Language) ą) including Polish(?) variable names mixed with English ... ;-) update `s/kandydat/contestant/` # "unpolished" variable name ;) as choroba++ already noted: write is a bad choice, maybe better `put_out()` or just 'out()'?	[reply] [d/l] [select]
Re^2: Problem with parameters in subroutines by aatrox (Initiate) on Jun 02, 2014 at 12:21 UTC
Thanks for the answer. I have done as you said and i got Not a GLOB reference at dziala.pl error, sorry for my code i will repair it i wanted to translate it from polish to english but forgot to change working part withour subroutine :)	[reply]
Re^3: Problem with parameters in subroutines by LanX (Saint) on Jun 02, 2014 at 12:30 UTC
> ... from polish to english but forgot ... Look for me it doesn't matter how you name your variables as long as your code... has a consistent language and is working. (just don't expect it to be self-documenting for too many people ;) Regarding you error please post working code which reproduces the problem. Cheers Rolf ( addicted to the Perl Programming Language)	[reply]

update