gives the default value for arguments of the function f obtained with a _. pattern object.


gives the default value to use when _. appears as the i^(th) argument of f.


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


defines default values for arguments of f.


  • _. 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].


Basic Examples  (1)

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

_. represents an argument that can be omitted:

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

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

Introduced in 1988