RuntimeError command

I am trying to build a mesh library and almost in every function I check for the existence of an argument

Function MyFunction(t.MyType, ...)

  if t = Null then RuntimeError "MyFunction: t does not exists!" : Return
.
.
.

End Function

I am wondering if this practice is a bottle neck to the execution speed. On the other hand I think it is not right to build a library without error check.

I would do:

Function MyFunction(t.mytype)
  if t <> null
    ;do stuff with t
  endif
end function

In other words - error checking, yes. Pointless error messages that ultimately nobody will see, no.

Also, nothing after RuntimeError will get executed, so the Return is redundant in this case.

I don't think you're checking the existance of an argument this way, but simply if it is zero. You can only use an argument optionally if you declare a default value:

function test(a=0)

But if you really want to test if an argument is used,you maybe have to set the default to a value that makes absolutely no sense and is completely unlikely to be used, eg:

function test(a=$FEFEFEFE)
if a=$FEFEFEFE then ; no argument was received

This example makes sense if the value will always be in a lower range. Right now I have no idea how to handle this savely if the entire 32 bit range should be usable.

GfK: if you return with a Null t you have to face it later in the program flow...
jfk EO-1110: Checking a pointer to see if it is zero the you get an "Illegal type conversion" from Blitz3D
I am still wondering if its worth error checking within every function in a library...

Yes Moraldi that is good practice. I almost always do it.
I usually have a DEBUG constant that I turn off when I build the EXE.

Function MyFunction(t.MyType, ...)

  If DEBUG If t = Null then RuntimeError "MyFunction: t does not exists!"
.
.
.

End Function

Total overkill in my opinion but probably good practice to have all this kind of error trapping.

Surely you know immediately if your passing a duff type to a function?

Stevie

Nah, sometimes you have like:

Function MyFunction(t.MyType, ...)
unit\target=t
Endfunction

then somewhere else you find out unit\target=null
Basically things can get complicated before you ever try to actually use the null instance.