RFC: Unicode primes and super/subscript characters in GHC

Mikhail Vorozhtsov mikhail.vorozhtsov at gmail.com
Tue Jun 17 12:55:55 UTC 2014

On 06/17/2014 03:13 AM, Tsuyoshi Ito wrote:
> Hello,
> Mikhail Vorozhtsov <mikhail.vorozhtsov at gmail.com> wrote:
>>> I also worry (although not based on anything particular you said)
>>> whether this will not change meaning of any existing programs. Does it
>>> only allow new programs?
>> As far as I can see, no change in meaning. Some hacky operators and some
>> hacky identifiers would become illegal. And some nicer ones would become
>> legal.
> I do not have an opinion for or against the proposal, but I just
> wanted to point out that the proposal changes the meaning of some
> programs, at least in theory.  The following function currently
> evaluates to True, but with the proposed change, I think that it will
> evaluate to False.
> test =
>    let a = ()
>        b = ()
>        a′b = False in
>    let c′d = True in
>    a′b
> Best regards,
> Tsuyoshi
Good catch. Indeed, PRIME will no longer be a valid operator.

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