Malcolm Wallace wrote:
"Brian Hulley" <[EMAIL PROTECTED]> wrote:
Thanks for pointing this out. Although there is still a problem with
the fact that var, qvar, qcon etc is in the context free syntax
instead of the lexical syntax so you could write:
2 ` plus ` 4
( Prelude.+
{- a comment -} ) 5 6
You appear to be right. However, I don't think I have ever seen a piece
of code that actually used the first form. People seem to naturally
place the backticks right next to the variable name. Should we consider
the fact that whitespace and comments are permitted between backticks to
be a bug in the Report? It certainly feels like it should be a lexical
issue.
I tend in the other direction: I'd rather see as much as possible pushed
into the context-free syntax. The only reason that qualified
identifiers are in the lexical syntax currently is because of the clash
with the '.' operator.
I'm not sure I can concisely explain why I think it is better to use the
context-free syntax than the lexical syntax, but I'll try. I believe
the lexical syntax should adhere, as far as possible, to the following rule:
juxtaposition of lexemes of different classes should not affect
the lexical interpretation.
in other words, whitespace between different lexemes is irrelevant. I
know this rule is violated in many places in the Haskell lexical syntax,
but at least for me it serves as a guideline for what is tasteful. For
example, it rules out `x` as a lexeme, because ` ought to be a reserved
symbol, and then `x` would be a justaposition of 3 lexemes. This also
explains to me why I think many of GHC's syntactic extensions are ugly
(42#, (#..#), $x, [d|..|], etc.). However, it's really hard to extend
the lexical syntax and stick to this rule, especially if you want to add
brackets. So you should consider this a rant, nothing more.
Cheers,
Simon
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