Word description Defines a callback from C to Factor which accepts the given set of parameters from the C caller, pushes them on the data stack, calls the quotation, and passes a return value back to the C caller. A return type of void indicates that no value is to be returned.
When a compiled reference to this word is called, it pushes the callback's alien address on the data stack. This address can be passed to any C function expecting a C function pointer with the correct signature. The callback is actually generated when the word calling alien-callback is compiled.
Callback quotations run with freshly-allocated stacks. This means the data stack contains the values passed by the C function, and nothing else. It also means that if the callback throws an error which is not caught, the Factor runtime will halt. See Exception handling for error handling options.