2010/5/21 R J <[email protected]>:
> Why does the following, trivial code snippet below hang GHCi when I type
> "Scalene > Failure", and what's the fix?
An instance of Ord must declare compare or (<=). You only defined (<),
so (>) is using the default definition. Here are the defaults:
compare x y = if x == y then EQ
else if x <= y then LT
else GT
x < y = case compare x y of { LT -> True; _ -> False }
x <= y = case compare x y of { GT -> False; _ -> True }
x > y = case compare x y of { GT -> True; _ -> False }
x >= y = case compare x y of { LT -> False; _ -> True }
max x y = if x <= y then y else x
min x y = if x <= y then x else y
Note that the default definitions of (<=) and compare call each other,
leading to an infinite loop when both are used.
Simple fix: define (<=) instead of (<).
--
Dave Menendez <[email protected]>
<http://www.eyrie.org/~zednenem/>
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