Function Precedence Order

This topic explains how MATLAB® determines which function to call when multiple functions in the current scope have the same name. The current scope includes the current file, an optional private subfolder relative to the currently running function, the current folder, and the MATLAB path.

MATLAB uses this precedence order:

  1. Variables

    Before assuming that a name matches a function, MATLAB checks for a variable with that name in the current workspace.

    Note

    If you create a variable with the same name as a function, MATLAB cannot run that function until you clear the variable from memory.

  2. Function or class whose name matches an explicitly imported name

    The import function allows functions with compound names (names comprised of several parts joined by dots) to be called using only the final part of the compound name. When a function name matches an explicit (non-wildcard) imported function,​ MATLAB uses the imported compound name and gives it precedence over all other functions with the same name.

  3. Nested functions within the current function

  4. Local functions within the current file

  5. Function or class whose name matches a wildcard-based imported name

    When a function name matches a wildcard-based imported function,​ MATLAB uses the imported compound name and gives it precedence over all other functions with the same name,​ except for nested and local functions.

  6. Private functions

    Private functions are functions in a subfolder named private that is immediately below the folder of the currently running file.

  7. Object functions

    An object function accepts a particular class of object in its input argument list. When there are multiple object functions with the same name, MATLAB checks the classes of the input arguments to determine which function to use.

  8. Class constructors in @ folders

    MATLAB uses class constructors to create a variety of objects (such as timeseries or audioplayer), and you can define your own classes using object-oriented programming. For example, if you create a class folder @polynom and a constructor function @polynom/polynom.m, the constructor takes precedence over other functions named polynom.m anywhere on the path.

  9. Loaded Simulink® models

  10. Functions in the current folder

  11. Functions elsewhere on the path, in order of appearance

When determining the precedence of functions within the same folder, MATLAB considers the file type, in this order:

  1. Built-in function

  2. MEX-function

  3. Simulink model files that are not loaded, with file types in this order:

    1. SLX file

    2. MDL file

  4. App file (.mlapp) created using MATLAB App Designer

  5. Program file with a .mlx extension

  6. P-file (that is, an encoded program file with a .p extension)

  7. Program file with a .m extension

For example, if MATLAB finds a .m file and a P-file with the same name in the same folder, it uses the P-file. Because P-files are not automatically regenerated, make sure that you regenerate the P-file whenever you edit the program file.

To determine the function MATLAB calls for a particular input, include the function name and the input in a call to the which function.

Change in Rules For Function Precedence Order

Starting in R2019b, MATLAB changes the rules for name resolution, impacting the precedence order of variables, nested functions, local functions, and external functions. For information about the changes and tips for updating your code, see Update Code for R2019b Changes to Function Precedence Order.

  • Identifiers cannot be used for two purposes inside a function

  • Identifiers without explicit declarations might not be treated as variables

  • Variables cannot be implicitly shared between parent and nested functions

  • Change in precedence of compound name resolution

  • Anonymous functions can include resolved and unresolved identifiers

The behavior of the import function has changed.

  • Change in precedence of wildcard-based imports

  • Fully qualified import functions cannot have the same name as nested functions

  • Fully qualified imports shadow outer scope definitions of the same name

  • Error handling when import not found

  • Nested functions inherit import statements from parent functions

See Also

Related Topics