Hi there. I'm a teacher of Maths and am working my way through the Euler
Project problems for fun. I have mostly been using Basic, but have read
up about Haskell and think it looks like a sensible way to solve many of
the problems.
OK, so I've downloaded GHCi and am trying to teach myself.
So far I have done this:
___ ___ _
/ _ \ /\ /\/ __(_)
/ /_\// /_/ / / | | GHC Interactive, version 6.6.1, for Haskell 98.
/ /_\\/ __ / /___| | http://www.haskell.org/ghc/
\____/\/ /_/\____/|_| Type :? for help.
Loading package base ... linking ... done.
Prelude> let f (a,b) = a * floor (100000/b)
Prelude> f(2,5)
40000
This function works just as I want it to.
Now I try creating a list:
Prelude> [(a2+b2,a)| a <- [1..4] , b<- [1..4], a2+b2<20, b<=a]
[(2,1),(5,2),(8,2),(10,3),(13,3),(18,3),(17,4)]
and this works
So now I try to apply the function to the list:
Prelude> map (f) [(a2+b2,a)| a <- [1..4] , b<- [1..4], a2+b2<20, b<=a]
and I get this result:
<interactive>:1:5:
Ambiguous type variable `t' in the constraints:
`Integral t' arising from use of `f' at <interactive>:1:5
`RealFrac t' arising from use of `f' at <interactive>:1:5
Probable fix: add a type signature that fixes these type variable(s)
I'm sorry, but I don't quite get how to set the type signature and how
it will apply to my function...
Thanks,
Tomi
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