OpenEuphoria

Re: Variable Arguments?

• Posted by yuku <yuku at ?k?tek.com> Apr 22, 2008
• 620 views

CChris wrote:
> 
> Jeremy Cowgar wrote:
> > 
> > CChris wrote:
> > > 
> > > The change was not trivial because it involves the ability to replay
> > > canned
> > > tokens after recording them. Indeed
> > > procedure foo(integer n=n0)
> > > needs late binding
> > >
> > 
> > Even something as simple as:
> > 
> > }}}
<eucode>
> > procedure foo(opt object n)
> > </eucode>
{{{

> > 
> > and if n was not supplied, n defaulting to NULL would be a huge step.
> > 
> > }}}
<eucode>
> > function round(sequence items, opt object n)
> >   if n = NULL then n = 1 end if
> >   ... code for round_precision ...
> > end function
> > </eucode>
{{{

> > 
> > That's not as good as function round(sequence items, integer precision=1)
> > but,
> > it's a huge step above what we have now and could be maintained later once
> > an
> > assignment would be possible.
> > 
> > How hard is something like that?
> > 
> What is NULL?
> If we had a nil object, as I have advocated for a long time, then it would be
> ok. But adding nil is trickier I think - or not, I haven't tried yet. Moving
> to 3-way logic might break too much code.

Instead of having a variable arguments or null type, I agree with JCougar,
having default arguments will be easier to understand and easier to implement.

How about this syntax (as intuitive as possible)

[global] {function|procedure} <name> ( [<type> <name>]* [<type> <name> = <def>]*
)

where <def> indicates default argument and it must be a constant!
Default arguments also must be the last in the argument list.

Then, instead of modifying the back end, we can only modify the front end,
to make it act like a preprocessor. e.g. for

global function round(object item, integer prec = 0)

, if the call is like round(2.54), the front-end will emit IL that is 
exactly the same as if the code were round(2.54, 0).


yuku