From a MATLAB® function, you can call local functions, supported toolbox functions, and other MATLAB functions. MATLAB resolves function names for code generation as follows:
The diagram illustrates key points about how MATLAB resolves function calls for code generation:
Searches two paths, the code generation path and the MATLAB path
Attempts to compile functions unless the code generation software determines that it should not compile them or you explicitly declare them to be extrinsic.
If a MATLAB function is not supported for code generation, you can declare it to be extrinsic by using the construct coder.extrinsic, as described in Declaring MATLAB Functions as Extrinsic Functions. During simulation, the code generation software generates code for the call to an extrinsic function, but does not generate the function's internal code. Therefore, simulation can run only on platforms where MATLAB software is installed. During standalone code generation, MATLAB attempts to determine whether the extrinsic function affects the output of the function in which it is called — for example by returning mxArrays to an output variable. Provided that the output does not change, MATLAB proceeds with code generation, but excludes the extrinsic function from the generated code. Otherwise, compilation errors occur.
The code generation software detects calls to many common visualization functions, such as plot, disp, and figure. The software treats these functions like extrinsic functions but you do not have to declare them extrinsic using the coder.extrinsic function.
Resolves file type based on precedence rules described in Resolution of File Types on Code Generation Path
During code generation, function calls are resolved on two paths:
Code generation path
MATLAB searches this path first during code generation. The code generation path contains the toolbox functions supported for code generation.
If the function is not on the code generation path, MATLAB searches this path.
MATLAB applies the same dispatcher rules when searching each path (see Function Precedence Order).