MathScript identifies user-defined functions by filename. The name of the file must be the same as the name of the function.
You can call user-defined functions from MathScript code inside a MathScript Node or from another user-defined MathScript function. Both the MathScript Node and the user-defined functions must be in your project. You cannot define multiple functions in one .m file.
Use the input and output arguments defined by a function definition in order to call the user-defined function. If you have, for example, a user-defined function named sumdifference.m in your project, use the following syntax to call the function from the MathScript Node:
[sum, difference] = sumdifference(5, 9)