November 2004 - Hugs-Bugs

Undefined variable bug
by John Tromp 27 Feb '07

27 Feb '07

I just found out that I can circumvent the problem by adding a line import Char to my loaded file. regards, -john

2 1

[Hugs-bugs] trying to build hugs98-20041101 on Linux
by Victor Secarin 10 Nov '04

10 Nov '04

Hello, all: I have been trying to build hugs on varoius RedHat platforms. While hugs98-Nov2002 works for me, anything newer fails. I am currently playing with hugs98-20041101. It seems to configure well (with ./configure ), and then tells me to do "make ; make install'. That however always breaks, ending in the following: cd .. ; env HUGSDIR='hugsdir' HUGSFLAGS=' ' src/ffihugs +G +L'hugsdir/libraries/Hugs/Storable_aux.c' Hugs.Storable make[1]: *** [../hugsdir/libraries/Hugs/Storable.so] Error 1 This seems like it should be the last step in the libraries/Makefile That is, the src is built, it also seems that the convert_libraries finishes, and then it tries to build Storable.so under hugsdir/libraries/Hugs/ and there ffihugs fails. The debugger revealed that ffihugs first tries to open Hugs.Prelude, which it finds, as hugsdir/libraries/Hugs/Prelude.hs, and then it also tries to find Prelude , which ought to be hugsdir/libraries/Prelude.hs (or something); it fails to find that file and it bails returning error code 1. In the hugs98-Nov2002, there is both a libraries/Hugs/Prelude.hs (large) and a libraries/Prelude.hs (small, includes the former). Is there a file missing? Am I doing something wrong? Please help, Victor Secarin

1 0

[Hugs-bugs] monomorphism bug
by Ross Paterson 01 Nov '04

01 Nov '04

I can't track this one down, so I'll post it: Prelude> :t let f = const 1 in let g = f in g let {...} in (let {...} in g) :: Num a => b -> c The error here is that a and c should be identified. In larger examples, this can cause real trouble. More detail: f is subject to the Monomorphism Restriction, so its return type should be monomorphic. Hugs gets this right, as seen in Prelude> :t let f = const 1 in (f,f) let {...} in (f,f) :: Num a => (b -> a,c -> a) However it loses the constraint on the type of g, as seen in Prelude> :t let f = const 1 in let g :: a -> b; g = f in g let {...} in (let {...} in g) :: Num a => b -> c (which it should reject). It seems essential that the type of f contain fully polymorphic variables as well as the constrained one.

1 0