[m-rev.] lex and moose changed

[Holger Krug]

On Thu, Aug 02, 2001 at 02:40:32AM -0700, Ralph Becket wrote:
> > Great proposal. Thanks ! I'll try to answer for both sides and allow
> > Ralph to kill me (but only within 3 hours after having read this email
> > and only personally, so he had to come to Berlin within 3 hours) if
> > there's some wrongdoing concerning his approach.
> 
> Damn, I'll never get a flight now!

Thanks heaven, no distant hypnosis.

> I feel there's a little bit too much going on here, but looking at it
> things don't seem nearly as bad as I'd imagined.

What do the others say ?
 
> I've got some minor suggestions for improving the syntax if this is
> the preferred option.
> 
> Rather than the somewhat bulky lexeme(AnnotatedToken, RegExp) we
> might want to move to a more traditional looking form, something
> like
> 
> lexemes = [
> 	atom('+')         - return(plus),
>       atom('-')         - return(minus),
> 	...
> 	signed_int        - (func(IStr) =
> int(string__det_to_int(IStr))),
>       identifier        - (func(Id)   = ident(Id))
> ].
> 
> Where we have return/2 as a utility function:
> 
> :- func return(T, string) = T.
> return(Token, _) = Token.

OK, looks nice.
 
> This would require extracting the string component for every matched
> regexp, but that's surely small beer in performance terms.

At the end of the times we will have a great optimizer which even
recognizes that those strings are never accessed ...
 
> Okay, I'm sold on the idea!

Great. It's free today.
 
> While we're at it, I suggest changing the regex operator names
> {/\, \/, star, plus, opt} to {++, or, *, +, ?} respectively.

I'm with this. 
 
> > % A problem here, I admit, is that in the current 
> > implementation there 
> > % is no way to signal an error at this  place in the case of e.g. an 
> > % integer overflow. This has to be added to the implementation. 
> > % (An exception may be thrown inside the converter. If the converter 
> > % throws an exception, `lex__read' catches the exception and returns 
> > % the appropriated error message. This all is transparent to 
> > the user, 
> > % I only forgot to implement it.)
> 
> Yes, I'd go along with that.

I now wait for additional remarks. If no further remarks come, I'll implement
the changes as proposed by you. OK ?

-- 
Holger Krug
hkrug at rationalizer.com
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