matlab uses "which" to find a file that shows up as a built-in function location, but why doesn't the file actually exist?

which some-built-in-function

'some-built-in-function' not found.

filename = "some-built-in-function-path";
if isfile(filename)
     disp("this file exist")
else
     disp("this file not exist")
end

this file not exist

so why does the actual file not exist? How do I understand what the file is "doing", or is it something like a mex file?

Answer 1

[Steven Lord]

Functions that which reports as built-in are compiled into the various binary files that make up MATLAB. If you're trying to find those files to read or modify the source code that is not possible. We do not distribute the source code for built-in functions.