MATLAB Programming

MATLAB Functions
The exist function also returns 2 for files that have a file type unknown to
MATLAB. However, if you invoke exist on a MATLAB function name, the file
type will be known to MATLAB and will return 2 only on M-files.
Viewing the Source Code
One advantage of functions implemented as M-files is that you can look
at the source code. This may help when you need to understand why the
function returns a value you didn’t expect, if you need to figure out how to
code something in MATLAB that is already coded in a function, or perhaps to
help you create a function that overloads one of the MATLAB functions.
To find the source code for any MATLAB M-file function, use which:
which repmat
D:\matlabR14\toolbox\matlab\elmat\repmat.m
Built-In Functions
Functions that are frequently used or that can take more time to execute are
often implemented as executable files. These functions are called built-ins.
Unlike M-file functions, you cannot see the source code for built-ins. Although
most built-in functions do have an M-file associated with them, this file is
there mainly to supply the help documentation for the function. Take the
reshape function, for example, and find it on the MATLAB path:
which reshape
D:\matlabR14\toolbox\matlab\elmat\reshape.m
If you type this M-file out, you will see thatitconsistsalmostentirelyofhelp
text. At the bottom is a call to the built-in executable image.
Identifying Built-In Functions
As with M-file functions, you can identify which functions are built-ins using
the exist function. This function identifies built-ins by returning the number
5:
exist reshape
ans =
5
3-111