instance inference

Bulat Ziganshin bulatz at
Mon Feb 6 09:49:42 EST 2006

Hello Ross,

Monday, February 06, 2006, 2:35:40 PM, you wrote:
RP> A patch implementing a relaxed termination constraint is at


[this patch provides the following:]

RP>  With -fglasgow-exts but not -fallow-undecidable-instances

RP>   (1) no variable has more occurrences in the assertion than in the
RP>       head, and
RP>   (2) the assertion has fewer constructors and variables (taken together
RP>       and counting repetitions) than the head.

i always thinks that existing rules too restrictive and something like
just counting chars at the left and right should be used ;)

one question - will be the same rules incorporated in Hugs? as you
know, i'm trying to made Hugs+GHC compatible library, so this matters

it will be even better if such improvement could be made to other
Haskell compilers and included in Haskell-prime standard. class system
of H98 and existing compilers is especially restricting flight of my
imagination :)

Best regards,
 Bulat                            mailto:bulatz at

More information about the Glasgow-haskell-users mailing list