Optional Arguments

[Phantomas]

Example of Procedure with some Optional Arguments:

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Procedure.i proc(one.i, two.i = 1337, three.i = 1337)
  Debug one
  Debug two
  Debug three
EndProcedure

What if I want call this procedure with declare only first (one) and third (three, optional) arguments? I do not want declare second (two, optional) parameter and want keep it default (1337).

In PAWN I can do that:

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proc(0, _, 1338)

"_" means "skip it" and this argument will be equal 1337.

In PureBasic I can not do that:

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proc(0, 1337, 1338)

I should enter second parameter and can not skip it.

[Tenaja]

No, but if you hardcode the default value in the definition, you can hardcode the value in the call. (Best with a pre-defined #Constant.)

[Little John]

When using named parameters for a procedure, the order of the parameters doesn't matter, and thus handling of optional parameters is very flexible. It can be implemented e.g. this way (at the expense of speed).

[Josh]

"_" means "skip it" and this argument will be equal 1337.

Think is a useful feature and not hard to implement in PB

+1

[c4s]

+1 for any kind of implementation.

But how about just keeping the desired optional argument empty (instead of using "_") as requested and discussed e.g. here: Procedures - optional parameter more flexible?! That would probably be even easier and more reasonable to implement because "_" is a valid variable name.

[Trond]

If the optional parameter can't have the value -1, it can be coded like this:

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#_ = -1

Procedure.i proc(one.i, two.i = 1337, three.i = 1337)
  If two = #_
    two = 1337
  EndIf
  Debug one
  Debug two
  Debug three
EndProcedure

proc(0, #_, 1338)

[Fred]

Yes, in PB we often use this as well trough the #PB_Ignore or #PB_Default constant.