[Haskell-cafe] rounding errors with real numbers.

[Matthias Fischmann]

> cancellation happens for instance here: 1 + 1e-50 - 1 == 0

the function again (in the wasteful original form, for clarity).
where do you think cancellation may take place?  isn't what you call
canellation a generic rounding error?

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

normInterval :: [Double] -> Double -> Double -> [Double]
normInterval ps lower upper = repair (map (\ x -> (x - oldLower) * stretch + lower) ps)
    where
    oldLower = head ps
    oldUpper = last ps
    stretch = (upper - lower) / (oldUpper - oldLower)

    -- fix rounding error:
    repair [i] = [upper]
    repair (h:t) = h : repair t

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

> >>(x-oldLower)*a + (oldUpper-x)*b

i got this into my head though.  neat.  thanks!  i will rewrite the
function right now.

cheers,
matthias
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 189 bytes
Desc: Digital signature
Url : http://www.haskell.org//pipermail/haskell-cafe/attachments/20060302/4550cd23/attachment.bin