How to tell if a function is built-in or self-defined by its name?

I generate a call graph of a complex MATLAB system, and I want to know which functions are built-in and mark them.

Although I think solutions based on which are better, for completeness, we should also consider the function exist for this. From the documentation:

exist name returns the type of name as a number. This list describes the type associated with each value:

• 0 — name does not exist or cannot be found for other reasons. For example, if name exists in a restricted folder to which MATLAB® does not have access, exist returns 0.

• 1 — name is a variable in the workspace.

• 2 — name is a file with extension .m, .mlx, or .mlapp, or name is the name of a file with a non-registered file extension (.mat, .fig, .txt).

• 3 — name is a MEX-file on your MATLAB search path.

• 4 — name is a loaded Simulink® model or a Simulink model or library file on your MATLAB search path.

• 5 — name is a built-in MATLAB function. This does not include classes.

• 6 — name is a P-code file on your MATLAB search path.

• 7 — name is a folder.

• 8 — name is a class. (exist returns 0 for Java classes if you start MATLAB with the -nojvm option.)

So when we try this on the examples shown earlier:

>> exist eig
ans =
     5
>> exist solve
ans =
     2
>> exist nosuchfunction
ans =
     0