
Algebra.NonNegative  Portability  Haskell 98  Stability  stable  Maintainer  haskell@henningthielemann.de 



Description 
A type class for nonnegative numbers.
Prominent instances are Numeric.NonNegative.Wrapper.T and peano numbers.
This class cannot do any checks,
but it let you show to the user what arguments your function expects.
In fact many standard functions (take, '(!!)', ...)
should have this type class constraint.
Thus you must define class instances with care.


Synopsis 

class (Ord a, C a) => C a where  


Documentation 


Instances of this class must ensure nonnegative values.
We cannot enforce this by types, but the type class constraint NonNegative.C
avoids accidental usage of types which allow for negative numbers.
  Methods   x  y == max 0 (xy) The default implementation is not efficient,
because it compares the values and then subtracts, again, if safe.
max 0 (xy) is more elegant and efficient
but not possible in the general case,
since xy may already yield a negative number.

  Instances  


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