With MATLAB®, you can generate reusable code in the following ways:
Write reusable functions using standard MATLAB function file names which you can call from different locations, for example, in a Simulink® model or MATLAB function library.
Compile external functions on the MATLAB path and integrate them into generated C code for embedded targets.
See Resolution of Function Calls for Code Generation (MATLAB Coder).
Common applications include:
Overriding generated library function with a custom implementation.
Implementing a reusable library on top of standard library functions that can be used with Simulink.
Swapping between different implementations of the same function.