#4430: Better support for resolving infix expressions in template haskell
---------------------------------+------------------------------------------
Reporter: reinerp | Owner: reinerp
Type: feature request | Status: new
Priority: normal | Milestone:
Component: Template Haskell | Version: 6.12.3
Keywords: | Testcase:
Blockedby: | Difficulty:
Os: Unknown/Multiple | Blocking:
Architecture: Unknown/Multiple | Failure: None/Unknown
---------------------------------+------------------------------------------
Comment(by simonpj):
Good point. I've thought about this a bit. I suggest we use the
{{{
data Exp = ...
| UnresolvedInfixE
Exp -- Left
Exp -- Operator
Exp -- Right
| Parens Exp
...
}}}
Reasoning
* It's simple, direct, and understandable.
* It is what GHC itself already does
* It is easy on the chap ''constructing'' the code. A parser is only
going to see one infix operator at a time, so building that list of
operands (the alternative approach) would be awkward.
* `UnresolvedInfixE` doesn't need to support sections, because `InfixE`
can do the job. If you write
{{{
InfixE
Nothing
op1
(UnresolvedInfixE e1 op2 e2)
}}}
then there should be an error if the fixity of `op1` and `op2` don't
relate correctly. To avoid this check, use `Parens`, or `InfixE` for the
inner constructor. (Of course the docs should state this.)
I think that leads to a simple, understandable design.
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/4430#comment:8>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
_______________________________________________
Glasgow-haskell-bugs mailing list
[email protected]
http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
