MATLAB Programming

4 M-File Programming
Determining Which Function Is Called
When more than one function has the same name, which one does MATLAB
call? This sectionexplainstheprocessthatMATLABusestomakethis
decision. It covers the following topics:
• “Function Scope” on page 4-54
• “Precedence Order” on page 4-54
• “Multiple ImplementationTypes”onpage4-56
• “Querying Which Function MATLAB Will Call” on page 4-56
Also keep in mind that there are certain situations in which function names
can conflict with variables ofthesamename. See“PotentialConflictwith
Function Names” on page 3-8for more information.
Function Scope
Any functions you call must first be within the scope of (i.e., visible to) the
calling function or your MATLAB session. MATLAB determines if a function
is in scope by searching for the function’s executable file according to a certain
order (see “Precedence Order” on page 4-54).
One key part of this search order is the MATLAB path. The path is an
ordered list of directories that MATLAB defines on startup. You can add or
remove any directories you want from the path. MATLAB searches the path
for the given function name, starting at the first directory in the path string
and continuing until either the function file is found or the list of directories
is exhausted. If no function of that name is found, then the function is
considered to be out of scope and MATLAB issues an error.
Precedence Order
The function precedence order determines the precedence of one function
over another based on the type of function and its location on the MATLAB
path. MATLAB selects the correct function for a given context by applying the
following function precedence rules in the order given here.
For items 3 through 7 in this list, the file MATLAB searches for can be any
of four types: an M- or built-in file, preparsed M-file (P-Code), compiled
4-54