readFloat

[Ch. A. Herrmann]

Hi Haskellers,

>>>>> "Max" == Max Kirillov <max630@mail.ru> writes:

    Max> So why one might need it? I've never used Rational, but, if
    Max> asked, I would say that they are for exact representation of
    Max> numbers (some symbolic calcs).

that's true. I'm using rationals intensively since a couple of years for this
purpose and I'd like that they remain as exact as they are. 

    Max> On the other side, 'real' dotted
    Max> numbers always represent some real values with finite
    Max> accuracy. 

I'm not sure if that always is the case, but there is the danger of
confusion and this should be enough reason to be careful.

    Max> That's look like a bad idea to me to call Rational
    Max> numbers 'real' and type (print) them as a decimal fraction (*).

Especially converting rationals to a string and back should always
be the identity. It would be better to print rationals in the
form       
       numerator % denominator

and read them in the same form.

Surely, it's good to have flexibility in a programming language;
but at critical points --and conversions between floating points
(even if represented as strings) and rationals are such a point-- 
a programming language should demand explicit conversion. 

Cheers
-- 
 Christoph