The enhanced parameter declaration and argument processing facilities first introduced in Maple 10 have been enhanced further. Improvements include the following:

You can declare optional parameters to raise an exception if the next argument does not match the declared type. If the next argument is missing, that is, there are no more arguments, then the default values are applied and no warning is issued.

Keyword parameters can specify alternative spellings of the keyword, such as color and colour, or have indexed names such as ${\mathrm{axis}}_1$, ${\mathrm{axis}}_2$, and so on. At procedure invocation time, keyword parameters are matched to arguments before positional and ordered parameters.

Using the new seq modifier, a single parameter can match a sequence of zero or more arguments of a specified type.

Dependent types (where the type of one parameter depends on the value of another) have been made explicit by the introduction of the depends modifier.

For details, see the parameter help page.