PROTO in sub NAME (PROTO) {
how is the (PROTO) operator in 'sub NAME (PROTO) {' supposed to be useful ?
sub foo {
sub foo ($) {
sub foo ($$) {
sub foo ($$$) {
sub foo ($@) {
sub foo (@) {
i see the relation to the amount of arguments supposed to be in @_ ---
my handy perl QRG provides a worthless explenation.
there doesnt seem to be any warning or error when you ($$$) but only provide
1 argument, for example.
Jeremy Kister
http://jeremy.kister.net/
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Re: PROTO in sub NAME (PROTO) {
Prototyping can be useful in Perl. It shouldn't be overused, however. They
can be powerful when trying to make functions that look and feel like
built-ins. Trying to, for example, create a subroutine that looks like map, grep, and
sort is made by prototyping it as (@) (will pass coderef and an array). If
you want to accept an array and handle it like splice does you can do (\@;@)
(will pass array ref and an optional array).
There are very specific examples found in the manual in perldoc perlsub.
And there is a warning IF the subroutine is declared before you call it.
Prototyping(1,2); #No exception, just a warning
sub Prototyping ($$$) {
print pop;
}
Prototyping 1, 2, 3; #Good job
Prototyping(1,2); #works, read perldoc perlsub
Prototyping(1); #Death
I'm an advocate of prototyping. I like the power it can display in making
your own functions behave like built-ins. But you can't go crazy with it and
prototype every sub you write. Only do it when it makes your and the
enduser's/maintainer's life easier.
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Re: PROTO in sub NAME (PROTO) {
On Sep 21, Jeremy Kister said:
how is the (PROTO) operator in 'sub NAME (PROTO) {' supposed to be useful ?
Prototypes are only useful:
1. when the function is prototyped BEFORE it is called,
2. when the function is called without an , and
3. when the function is not a method of an object.
See the documentation for prototypes. Chances are, you don't need them.
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