some Matlab functions are not implemented in their m files

Hello everyone, sometimes, in order to have a full grasp of what is happening, I just navigate through matlab functions and see their implementation. A few times I've ended in a function whose .m file is only comments and no implementation (e.g. matlab-path\toolbox\matlab\lang\feval.m) So I wonder, when I invoke that function, what happens?

Thanks

Answer 1

[Honglei Chen]

Those are built-in functions and the MATLAB file is only for the documentation purpose. When you call such functions, MATLAB knows what to launch.

[Daniel Shub]

Are they all builtins or can they be a mex also?

[Honglei Chen]

I'm not hundred percent sure but I think most of them should be built-ins. In general I think if there is a mex, you will see a call to mex in the file. If the mex does not need to be invoked, I personally would call them built-ins :)