Default

Default[f]

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^(th) argument of f.

Default[f,i,n]

gives the default value for the i^(th) argument out of a total of n arguments.

Default[f,…]=val

defines default values for arguments of f.

Details

  • _. 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 in DefaultValues[f].

Examples

Basic Examples  (1)

Define 0 to be the default argument for a function f:

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_. represents an argument that can be omitted:

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If the second argument is omitted, the default value of 0 is used instead:

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If both arguments are omitted, both are taken to have the default value 0:

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Introduced in 1988
(1.0)