I started this e-mail thread on HaskellCafe instead of HaskellPrime because it was minimal, backwards-compatible, valid Haskell 98 (or very nearly so) and could go (now) into GHC if someone saw fit to put it in.
If you think C++ is not overly complicated, just what is a protected abstract virtual base pure virtual private destructor, and when was the last time you needed one? -- Tom Cargil, C++ Journal
The above was not a proposal for Haskell'.
Proposers of new [C++] features should be required to donate a kidney. > That would - Jim [Waldo] pointed out - make people think hard before proposing, and even people without any sense would propose at most two extensions. -- Bjarne Stroustrup, creator of C++
But at the risk of losing a kidney... Here's where I think Haskell 98 got it wrong: "A fixity declaration may appear anywhere that a type signature appears and, like a type signature, declares a property of a particular operator." Like a type signature? A type signature has semantic value, fixity does not. In principle, neither does the name that a lambda abstraction is bound to in top-level definitions, but we are stuck with linkers that know about names. They don't know about fixity. Operator precedence is a purely syntactic device for people (like me) who hate parentheses. Its "scope" is essentially local to the attention span of a human being (i.e. a single module). A preprocessor can parethesize code to eliminate the need for fixity. I hate chasing other modules looking up operator fixity and would rather just specify it myself: What if we could remap fixity on import: -- (MyModule.???) fixity is 4, exported as its default... import MyModule((???)) -- But in this module I prefer 5... -- This fixity is *not* exported! infix 5 ??? Modules that import this module get the default fixity from the source. Summary: fixity at definition is exported, fixity on import is locally remapped but not reexported.
Better is the enemy of the good -- Voltaire
Simple, powerful, minimal. Any takers? Dan Dan Weston wrote:
Here's an idea that (I think) is useful and backwards compatible: fractional and negative fixity.
There have been 3 separate times where I've wanted an operator just above 0 ($) but less than 1 (>>= or >>>), or else just below 0 (like a superlow $$)
infix 0.5 ??? infix -1 $$
The only change would be internal to compiler, wouldn't it? Since fixity is just syntactic sugar, there should be no semantic difficulties.
Dan