Proposal (base): Add new Exp constructor to Text.Read.Lex.Lexeme

Christian Maeder Christian.Maeder at
Mon Dec 12 13:14:10 CET 2011

Am 12.12.2011 12:17, schrieb Gracjan Polak:
> Simon Marlow<marlowsd<at>>  writes:
>> Ok by me, though I'm not familiar with the details of
>> Text.Read.Lex.Lexeme.  I think it's an "internal" API of sorts, since it
>> was added to implement Text.Read.lex.
> If this API is internal then I'd propose to remove Rat constructor, as this one
> is ever used only with powers of 10 as denominator. And we would have that case
> covered better by Exp contructor.

How do you intent to store fractional numbers (like "10.01") without the 
Rat constructor?

How do you represent "10.01e10"?

    Exp Integer Integer

seems to be not enough.

In any case, "^" from the integer-gmp should not be used to compute a 
Rat value for the powers of 10. (see also


>> I wonder why integer-gmp crashes when trying to allocate too much...
>> sounds like we need to look into that - could you make a ticket if there
>> isn't already one?
> I've checked 6.12.3, where this problem appears. I've heard this issue is not
> present in 7.2, I'm going to check HEAD and see if I can reproduce the crash.

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