[REBOL] Re: A question of function interface design
From: andreas:bolka:gmx at: 19-Jan-2005 12:26
Wednesday, January 19, 2005, 12:17:54 PM, PeterWAWood wrote:
> I have started to question whether it is best to use Rebol's
> automatic type checking of parameters or not when designing
> functions.
> If the type checking is used, calling a function with an incorrect type of
> value causes a script error, eg:
> >> a: func [b [date!]] [print b]
> >> a 12345
> ** Script Error: a expected b argument of type: date
> ** Near: a 12345
> However, if you don't use the built-in type checking, you can return a none!
> value and give the caller the option (and responsibility) to deal with the
> situation, eg:
> >> a: func [b] [if type? b <> date! [return none]]
> >> a 12345
> == none
> Given that Rebol is not strongly typed, is the second of these
> "idioms" the more appropriate?
While the latter has obvious flaws when dealing with functions that
may validly return 'none, I can see no advantages whatsoever. If the
caller wants to deal with the situation, why not simply use 'try ? For
example
a: func [b [date!]] [print b]
if error? try [ a 12345 ] [ print "uh oh!" ]
--
Best regards,
Andreas
