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Parametric polymorphism

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Parametric polymorphism is when a function's type signature allows various arguments to take on arbitrary types, but the types most be ''related'' to each other in some way.
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#REDIRECT [[Polymorphism#Parametric polymorphism]]
 
For example, in Java one can write a function that accepts two arguments of any possible type. However, Haskell goes further by allowing a function to accept two arguments of any type so long as they are both ''the same'' type. For example
 
 
As a specific (and slightly more complicated) example, the well-known <hask>map</hask> function has a parametrically polymorphic type
 
 
<haskell>
 
map :: (a -> b) -> [a] -> [b]
 
</haskell>
 
 
which means that the function well accept ''any'' type of list and ''any'' type of function, '''provided''' the types match up. This makes <hask>map</hask> highly polymorphic, yet there is still no risk of a runtime type mismatch.
 

Latest revision as of 21:39, 4 September 2012

  1. REDIRECT Polymorphism#Parametric polymorphism