[Aldor-l] Semicolon after single statement in if?

[Pippijn van Steenhoven]

On Thu, May 07, 2009 at 01:22:59AM +0200, Ralf Hemmecke wrote:
>> Removing the ; from either of the two last lines will be fine. The only
>> thing it does not accept is ;; anywhere.
>
> That ;; is not accepted is somewhat strange. If I look at the grammar,  
> it says:
>
> Expression: enlist1a(Labeled, ";")
>
> So if ever you find a place in you program where "Expression" is  
> appropriate, then also ;; should be appropriate.

I was wrong. The compiler actually does accept ;;, but not ;;;.
Try:

  a := 3; -- works
  a := 3;; -- works
  a := 3;;;
  .......^
  (Error) Cannot recover from earlier syntax errors.

My (educated, since this happens all the time in the compiler) guess is
that the lexer has hacks to recover from ;; but it kills only one ;, so
the third ; is still read. All these hacks are getting me quite pissed..
Lexing a float, for instance:

  float: integer '.' [ integer ]
       | '.' integer

now notice the operator '.' and the operator '..' in:

  2..3

this could be either of:

  2. . 3
  2. .3
  2 . .3
  2 .. 3

so there is code that takes care of this. I currently use a lookahead
character to decide this, so if I read a float "2.", I look whether the
next character is '.' and if so, push back the '.' into the stream and
return an integer. NAG-Aldor has some more code for this to decide
whether floats can exist in certain lexical contexts. Does the AUG have
anything on this?

-- 
Pippijn van Steenhoven
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