[Haskell-beginners] how to print a floating-point number?
winitzki at gmail.com
Thu Jan 8 11:45:09 EST 2009
Subject: how to print a floating-point number?
I am very new to Haskell. I am trying to benchmark the CPU time needed
for a computation, and I can't figure out how to print a
My code is as follows, and I expected it to work:
main = do
let result = some_computation
time <- getCPUTime -- this is an Integer that needs
to be divided by 1e12 to get time in seconds
print (time / 1.0e12) -- I want this to print a
But this does not compile.
Error message: No instance for (Fractional Integer)
arising from use of `/' at fact1.hs:18:15-28
Possible fix: add an instance declaration for (Fractional Integer)
In the first argument of `print', namely `(time1 / 1.0e12)'
I thought this should work because e.g. 12 / 7 evaluates to
1.7142857142857142 in ghci.
I understand this is some problem with types, but surely it is fixed
not by adding any instance declarations but perhaps by using some
Prelude or Numeric function. But which one?
I tried everything I could find in the documentation: showFloat,
adding ::Float everywhere, adding fromIntegral, etc.etc. - nothing
works. All the books and the tutorials I looked at seem to discuss at
length such nice things as Fibonacci numbers and recursive factorial
functions rather than a practical problem like this.
help will be much appreciated!
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