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

argument of f.

Default[f, i, n]
gives the default value for the

argument out of a total of n arguments.

Default[f, ...]=val
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.

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: