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Abstract type: Difference between revisions
→{{header|Genyris}}
Line 112:
<lang python>class Stack()
def !valid?(object) nil
tag Stack some-object ; always fails</lang>
However this is not much use if we want to use an abstract class to define an interface. Here is a quasi-abstract class which can be used to tag objects if they conform to the class's membership expectations:
<lang python>class AbstractStack()
def !valid?(object)
object
and
bound? !enstack
is-instance? !enstack Closure
bound? !destack
is-instance? !destack Closure</lang>
=={{header|Haskell}}==
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