Matlab Types - Function Handle

Function Handle

A function handle is a data type that represents a Matlab Function. It lets you assign a function to a variable and use functions more flexibly. When invoked, a function handle behaves the same as the function it points to.

Note, however, that a function handle is only a reference to the original function; it does not store the function’s body. If the original function is removed, every handle pointing to it becomes invalid.

Properties

• functions returns detailed information about the function referenced by a handle
• isequal can compare two function handles
  • Operators such as == are not supported on function handles

Creation Syntax

fhandle = @funName

The operator @ converts the function funName into a function-handle value and assigns it to the variable fhandle.

• A space is allowed after @.

Anonymous Functions

A common use of function handles is to create single-line anonymous functions; see Matlab Anonymous Function.

As a Data Type

To build “function arrays” or “function structures”, you rely on the fact that a function handle is itself a data type. For example:

disp('sin',pi/2) % displays 1
 
function y = fun(which_fun,x)
s.sin = @sin; % store functions as handles inside a structure
s.cos = @cos;
y = s.(which_fun)(x);
end

Some functions accept a function as an argument (function functions); the input function must first be converted to a handle before being passed in:

Sin = @sin
disp(integral(Sin,0,pi)) % displays 2.0000

This is a property of the data type itself, so the handle does not have to be assigned to a variable — it can be used directly as a function-handle value:

disp(integral(@sin,0,pi)) % displays 2.0000
disp(integral(@(x) x.^2,0,1)) % displays 0.3333

For an anonymous function with no input arguments, you cannot omit the parentheses () the way you can with ordinary functions; otherwise the result is the handle’s variable information rather than a call:

>> f = @() disp('hello');
>> f()
hello
>> f
  function_handle with value:
    @()disp('hello')