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2.2.6 The function data type, part 2

There's one data type that I more or less ignored earlier, and that's the function type. Just as there's a type for objects, functions have a type as well. You can have function variables and call assigned functions through those variables. Mostly the function type is used in conjunction with other functions that use them as parameters.

You declare a function type just as any variable:

<data type> <variable name>, <another variable>, ..., <last variable>; e.g. function my_func, *func_array;

Assigning actual function references to them, however, is a bit tricker. You can assign any kind of function to a function variable; efun, sfun or lfun is just the same. You can even assign external function references.

Assigning a function reference requires that the function already is defined, either itself or by a function prototype in the header. Let's assume for now that you're only interested in the simple reference to the function.

<function variable> = <function name>; <function variable> = &<function name>(); e.g. my_func = allocate; my_func = &allocate();

Usage of the new function reference is done just as with the ordinary function call.

int *i_arr; i_arr = allocate(5); // Is the same as... i_arr = my_func(5); // ... using the function assignment above.

This will be enough for now. Later I'll explain how to create partial function applications, internal and external function declarations and how to use them in complex function combinations.