On Apr 23, 2009, at 11:28 , michael rice wrote:
<interactive>:1:0:
No instance for (Show (Seed -> (Int, Seed)))
arising from a use of `print' at <interactive>:1:0-9
Possible fix:
add an instance declaration for (Show (Seed -> (Int, Seed)))
In a stmt of a 'do' expression: print it
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Pretty much any time you get this kind of message, you've forgotten to include one or more arguments (how many is indicated by the number of "->"s) so ghci is trying to print a function.
In this case, while the definition of sumTwoDice *looks* like it doesn't take any arguments, if you look at the definition of the Random type, it is a function (in fact, the very type ghci is trying to print). You need to give it a seed before it will produce a result.