"numerator" and "denominator"

[Scott Turner]

On Tuesday 07 August 2001 04:45, Iain McNaughton wrote:
> However, when I try to use these functions on WinHugs, I get results
> like:
>         numerator 1.3 = 5452595
>         denominator 1.3 = 4194304
>
> This strikes me as strange, as what I was expecting was:
>         numerator 1.3 = 13
>         denominator 1.3 = 10

It's not Hugs's library that's having problems here, it's the way Hugs 
handles the literal 1.3.  I recall this being mentioned in the past, but it 
still doesn't seem to be listed among the bugs on the web site or the 
discrepancies in the manual.

Section 6.4.1 of the Haskell 98 report says, "a floating literal stands for 
an application of fromRational to a value of type Rational" where the latter 
value plainly needs to be, as you expect,    13 :% 10.

What Hugs is doing is immediately converting every floating literal to
a binary floating point number in machine form.  Since 1.3 is not
exactly representable in binary, an approximation is stored which
has the above ugly appearance if you inspect it as a rational
number.