|GNU Octave Manual Version 3|
by John W. Eaton, David Bateman, Søren Hauberg
Paperback (6"x9"), 568 pages
RRP £24.95 ($39.95)
11.2 Multiple Return Values
Unlike many other computer languages, Octave allows you to define functions that return more than one value. The syntax for defining functions that return multiple values is
function [ret-list] = name (arg-list) body endfunction
where name, arg-list, and body have the same meaning
as before, and ret-list is a comma-separated list of variable
names that will hold the values returned from the function. The list of
return values must have at least one element. If ret-list has
only one element, this form of the
function statement is
equivalent to the form described in the previous section.
Here is an example of a function that returns two values, the maximum element of a vector and the index of its first occurrence in the vector.
function [max, idx] = vmax (v) idx = 1; max = v (idx); for i = 2:length (v) if (v (i) > max) max = v (i); idx = i; endif endfor endfunction
In this particular case, the two values could have been returned as elements of a single array, but that is not always possible or convenient. The values to be returned may not have compatible dimensions, and it is often desirable to give the individual return values distinct names.
In addition to setting
nargin each time a function is called,
Octave also automatically initializes
nargout to the number of
values that are expected to be returned. This allows you to write
functions that behave differently depending on the number of values that
the user of the function has requested. The implicit assignment to the
ans does not figure in the count of output
arguments, so the value of
nargout may be zero.
lu functions are examples of built-in
functions that behave differently depending on the value of
It is possible to write functions that only set some return values. For example, calling the function
function [x, y, z] = f () x = 1; z = 2; endfunction
[a, b, c] = f ()
a = 1 b = (0x0) c = 2
along with a warning.
- Built-in Function: nargout ()
- Built-in Function: nargout (fcn_name)
- Within a function, return the number of values the caller expects to
receive. If called with the optional argument fcn_name, return the
maximum number of values the named function can produce, or -1 if the
function can produce a variable number of values.
nargoutto return 0 inside the function
[s, t] = f ()
nargoutto return 2 inside the function
At the top level,
See also nargin, varargin, varargout
- Function File: nargchk (nargin_min, nargin_max, n)
- If n is in the range nargin_min through nargin_max
inclusive, return the empty matrix. Otherwise, return a message
indicating whether n is too large or too small.
This is useful for checking to see that the number of arguments supplied to a function is within an acceptable range.
|ISBN 095461206X||GNU Octave Manual Version 3||See the print edition|