Re: weird macro params issue

On 2008.05.02., at 19:43, Jonathan Revusky wrote:

> I misspoke above. I meant, here, that it would be better if it always
> worked than if it worked some of the time and failed other times. I
> mean, it should always work or always fail... :-)
>
> JR
> but I think I would just tend towards it always failing.

What's funny is that I have an idea how to make it work whenever  
possible, but making it always fail seems less trivial, as you need to  
prove none of the default expressions actually depend on other  
parameters; i.e. you could have an argument list of "a  
b=someGlobalVar[a]"; you'd need to analyze the full default expression  
of 'b' for any occurrence of 'a', and then it can be even more hidden,  
like b=someGlobalVar[.local["a"]]; you get the idea. The "always work"  
would however cover even these horrors naturally :-)

It would have one last issue with not being deterministic with  
existence built-ins, i.e.

[#macro x a b=a c=b?default("foo")]
${c}
[/#macro]

[@x "bar"/]

would nondeterministically print either "foo" or "bar", which can be  
further rectified by always doing the evaluation in declaration order  
within every iteration. I guess that would have us covered... I *know*  
it'd be a godawful practice to use an existence builtin in defaulted  
arg list because the engine doesn't allow you to have any param be  
undefined, but these are still corner cases allowed by the language,  
so we'd better address them to be deterministic...

Attila.

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