Re: [boost] Re: Spirit syntax -- another suggestion.

From: joel de guzman (isis-tech_at_[hidden])
Date: 2001-05-31 06:42:18

From: "Vladimir Prus" :.

> 
> Complete, true. But is it the best? I find that prefix "*" and "+" are
> unnatural. "nonterminal(1, more)" for "+" is better, but overly verbose,
> "nonterminal-seq", in my opinion, is quite natural and consice notation.

Spirit uses the - for set difference:

  a - b;    a but -not- b

This is very useful IMO. XML uses this a lot for example, in its
grammar definition.

Also, based on user feedback (including novices), people find the prefix 
kleene star (*) and the prefix positive iterator (+) simple to comprehend.
I'll quote Andy Elvey:

<quote>
"Although I'm a newcomer to the parsing area, I thought I'd add my 2c 
worth anyway (on the theory that (hopefully!) a fresh and new pair of 
eyes from outside may be useful ."

 "I've found the current syntax of Spirit to be not confusing at all. 
Given that some with vastly more experience than me *may* find it 
confusing, I was wondering - would it be possible to have (say) a 
*flag* of some kind , so that users could have a *choice* of syntax?"
</quote>

Of course we cannot have a syntax switch. That would be a 
compatibility nightmare. The point is, Andy has no pre-conceived
notion of what should and shouldn't be. Which, I consider very
valuable.

So again, this issue is very subjective. What might be 'unnatural'
for some might not be so for others.

Cheers,
Joel de Guzman