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Parameters
ref parameters:
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One can use them to write methods with transient parameters, which are values
that are passed to a method, modified by the method, and returned to the caller.
If the same effect were to be achieved with functions one would have to use
both an input parameter and a function return value.
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One can use them to write methods with multiple transient parameters.
With functions, one can have only a single return value.
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The value of a ref parameter is not copied to the corresponding formal
parameter upon method call, but only a reference to the actual parameter
is passed. For large parameter objects this is more efficient than
passing the values of the objects.
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ref parameters can lead to side effects, because a formal ref parameter
is an alias of the corresponding actual ref parameter. If the method
modifies the formal ref parameter, the corresponding actual parameter
value changes as well.
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out parameters:
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One can use them to write methods with multiple output parameters.
With functions, one can have only a single return value.
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Like ref parameters, out parameters are passed by reference. This
means that only a reference to the actual parameter is passed and not
its value. For large parameter objects this is more efficient than
returning the value as a function result.
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The compiler makes sure that the invoked method assigns avlues
to all its out parameters.
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out parameters can lead to side effects, because a formal out parameter
is an alias of the corresponding actual out parameter. If the method
modifies the formal out parameter, the corresponding actual parameter
value changes as well.
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Function return values:
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There are no side effects. |
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The return value can be ignored by the caller. However, this can also
be regarded as a disadvantage.
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A function method can have only a single return value. |
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