Variable-length Argument Lists - Untitled
Description: Untitled

Next: Variable-length Return Lists, Previous: Multiple Return Values, Up: Functions and Scripts

### 11.3 Variable-length Argument Lists

Sometimes the number of input arguments is not known when the function is defined. As an example think of a function that returns the smallest of all its input arguments. For example,

         a = smallest (1, 2, 3);
         b = smallest (1, 2, 3, 4);

In this example both `a` and `b` would be 1. One way to write the `smallest` function is

         function val = smallest (arg1, arg2, arg3, arg4, arg5)
           body
         endfunction

and then use the value of `nargin` to determine which of the input arguments should be considered. The problem with this approach is that it can only handle a limited number of input arguments.

Octave supports the `varargin` keyword for handling a variable number of input arguments. Using `varargin` the function looks like this

         function val = smallest (varargin)
           body
         endfunction

In the function body the input arguments can be accessed through the variable `varargin`. This variable is a cell array containing all the input arguments. See Cell Arrays, for details on working with cell arrays. The `smallest` function can now be defined like this

         function val = smallest (varargin)
           val = min ([varargin{:}]);
         endfunction

This implementation handles any number of input arguments, but it's also a very simple solution to the problem.

A slightly more complex example of `varargin` is a function `print_arguments` that prints all input arguments. Such a function can be defined like this

         function print_arguments (varargin)
           for i = 1:length (varargin)
             printf ("Input argument %d: ", i);
             disp (varargin{i});
           endfor
         endfunction

This function produces output like this

         print_arguments (1, "two", 3);
              -| Input argument 1:  1
              -| Input argument 2: two
              -| Input argument 3:  3

— Function File: [reg, prop] = parseparams (params)

> Return in reg the cell elements of param up to the first string element and in prop all remaining elements beginning with the first string element. For example

>               [reg, prop] = parseparams ({1, 2, "linewidth", 10})
>               reg =
>               {
>                 [1,1] = 1
>                 [1,2] = 2
>               }
>               prop =
>               {
>                 [1,1] = linewidth
>                 [1,2] = 10
>               }

> The parseparams function may be used to separate 'regular' arguments and additional arguments given as property/value pairs of the varargin cell array.

> See also: varargin.