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Pure functions are required to construct pure expressions.
- It is possible for a pure expression to yield an impure function (or more generally a value which contains one or more impure functions).
- It is also possible for an expression to be pure even if one or more of the argument subexpressions yields an impure function (or a value which contains one or more impure functions).
} Foo is pure because it always returns the same function, but the function it returns is impure since it has the side effect of modifying the count variable. —Preceding unsigned comment added by GalaxiaGuy (talk • contribs) 13:24, 7 July 2010 (UTC)