[Haskell-cafe] First steps in Haskell
lemmih at gmail.com
Sun Dec 18 11:32:55 EST 2005
On 12/18/05, Daniel Carrera <daniel.carrera at zmsl.com> wrote:
> Hello all,
> I'm trying to write the simplest possible Haskell program, and I'm not
> getting anywhere.
> I have installed Hugs, GHC and GHCI. I want to run the following program:
> fac :: Integer -> Integer
> fac 0 = 1
> fac n | n > 0 = n * fac (n-1)
> This is what I see:
> $ hugs
> Hugs.Base> fac :: Integer -> Integer
> ERROR - Undefined variable "fac"
> Hugs.Base> fac 0 = 1
> ERROR - Syntax error in input (unexpected `=')
> $ ghci
> Prelude> fac :: Integer -> Integer
> <interactive>:1:0: Not in scope: `fac'
> Prelude> fac 0 = 1
> <interactive>:1:6: parse error on input `='
> $ # Write the program to fac.hs
> $ ghc fac.hs
> The main function `main' is not defined in module `Main'
> When checking the type of the main function `main'
GHC is a compiler. If you want to compile to a binary then you must
define a function called 'main'. Otherwise just load the file in ghci
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