Parameterized Implementations

Routine and method implementations, as well as classes, can be parameterized. Within the scope of a parameterized implementation, formal parameters can be used as types whose objects have only the methods and signatures indicated in the where clause. For example, in

find [T] (x: collection[T], v: T) returns (int) signals (not_found)
      where T has equal(T) returns (bool)
    w: T 
    ...
    if v = w ...   % short for v.equal(w)
    ...
    end find

the call "v.equal(w)" (made using the associated short form) is legal. Such method calls make sense because instantiations are only permitted for types whose objects have the required methods (3.2.2).

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