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  • Default[ f ], if defined, gives the default value for arguments of the function f obtained with a _. pattern object.
  • Default[ f , i ] gives the default value to use when _. appears as the i argument of f.
  • Default[ f , i , n ] gives the default value for the i argument out of a total of n arguments.
  • _. represents an optional argument to a function, with a default value specified by Default.
  • The necessary values for Default[ f ] must always be defined before _. is used as an argument of f.
  • Values defined for Default[ f ] are stored with the Options values of f.
  • See the Mathematica book: Section A.5.1.
  • See also: Options.
  • Related package: Utilities`FilterOptions`.