[bitc-dev] Issues for s-block surface syntax

[Kevin Reid]

On Jan 23, 2008, at 15:10, Jonathan S. Shapiro wrote:

> On Wed, 2008-01-23 at 19:52 +0000, Sam Mason wrote:
>> Haskell has a nice feature where any sequence of punctuation  
>> characters
>> is treated as an infix operator.
> ...
> I'm also not sure that this feature obeys lexical scoping  
> constraints. Does it? If not, then my negative opinion about it  
> goes up exponentially.

It most certainly does. Ordinary identifiers and 'operator  
symbols' (to use the language of the Haskell 98 Report) are identical  
except in parsing; the semantics do not vary, and each can be used in  
place of the other with appropriate markers.

http://www.haskell.org/onlinereport/lexemes.html

 From http://www.haskell.org/onlinereport/exps.html :
> An operator is either an operator symbol, such as + or $$, or is an  
> ordinary identifier enclosed in grave accents (backquotes), such as  
> `op`. For example, instead of writing the prefix application op x  
> y, one can write the infix application x `op` y. If no fixity  
> declaration is given for `op` then it defaults to highest  
> precedence and left associativity (see Section 4.4.2).
>
> Dually, an operator symbol can be converted to an ordinary  
> identifier by enclosing it in parentheses. For example, (+) x y is  
> equivalent to x + y, and foldr (*) 1 xs is equivalent to foldr (\x  
> y -> x*y) 1 xs.
>

-- 
Kevin Reid                            <http://homepage.mac.com/kpreid/>