Qualified identifiers opinion

Isaac Dupree isaacdupree at charter.net
Wed Aug 15 18:48:09 EDT 2007

Especially after writing a partial lexer for Haskell, I opine that this 
should be all legal:

module Foo where

--in case you didn't know, this is legal syntax:
Foo.f = undefined

Foo.mdo = undefined
Foo.where = undefined
x Foo.! y = undefined
x Foo... y = undefined --remember ".." is reserved id, e.g. [2..5]

{-# LANGUAGE RecursiveDo, BangPatterns #-} module Bar where
import Foo
hello !x = mdo { y <- Foo.mdo Foo... ({-Foo.-}f x y); return y }

{- Haskell 98 -} module Baz where
import Foo
goodbye x = x ! 12

(Foo.where) lexing as (Foo.wher e) or (Foo . where) does not make me 
happy.  (being a lexer error is a little less bad...)  Especially not 
when the set of keywords is flexible.  I don't see any good reason to 
forbid declaring keywords as identifiers/operators, since it is 
completely unambiguous, removes an extension-dependence from the lexer 
and simplifies it (at least the mental lexer); Also I hear that the 
Haskell98 lexing is (Foo.wher e), which I'm sure no one relies on...

Well, that's my humble opinion on what should go into Haskell' on this 


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