[Haskell-cafe] Non polymorphic numerals option -- avoiding type classes

[Rustom Mody]

On Thu, Dec 27, 2012 at 1:48 AM, Roman Cheplyaka <roma at ro-che.info> wrote:

> * Rustom Mody <rustompmody at gmail.com> [2012-12-26 20:12:17+0530]
> > So is there any set of flags to make haskell literals less polymorphic?
>
> Yes, there is!
>
>   % ghci -XRebindableSyntax
>   GHCi, version 7.6.1: http://www.haskell.org/ghc/  :? for help
>   Loading package ghc-prim ... linking ... done.
>   Loading package integer-gmp ... linking ... done.
>   Loading package base ... linking ... done.
>   > import Prelude hiding (fromInteger)
>   Prelude> let fromInteger = id
>   Prelude> :t 3
>   3 :: Integer
>
> Roman
>


Thanks Roman -- that helps.
And yet the ghci error is much more obscure than the gofer error:

--- contents of .ghci ---
:set -XRebindableSyntax
let fromInteger = id
------ ghci session -----
$ ghci
GHCi, version 7.4.1: http://www.haskell.org/ghc/  :? for help
Loading package ghc-prim ... linking ... done.
Loading package integer-gmp ... linking ... done.
Loading package base ... linking ... done.
Prelude> :t 5
5 :: Integer
Prelude> :t [[1,2],3]

<interactive>:1:8:
    Couldn't match expected type `[Integer]' with actual type `Integer'
    Expected type: Integer -> [Integer]
      Actual type: Integer -> Integer
    In the expression: 3
    In the expression: [[1, 2], 3]


----- The same in gofer -----
Gofer session for:
pustd.pre
? :t [[1,2],3]

ERROR: Type error in list
*** expression     : [[1,2],3]
*** term           : 3
*** type           : Int
*** does not match : [Int]
--------------
So the error is occurring at the point of the fromInteger (= id) but the
message does not indicate that

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