Synopsis

:- use_module(library(function_expansion)).
user:function_expansion(incr(N), X, X is N+1).
main :-
    format('After 2 comes ~p~n', [incr(2)]).

Description

Prolog doesn't offer function syntax. Anything one can do with functions, she can do with predicates. The syntax is a little verbose because it requires an auxiliary variable.

For example, one might approximate pi:

pi(3.14159).
main :-
    pi(Pi),
    format('pi is roughly ~p~n', [Pi]).

It's often obnoxious to think up a name for an auxiliary variable. function_expansion/3 lets you write macros so that pi can be included directly in format's arguments. Auxiliary variables are generated for you at compile time.

Repository available on GitHub: https://github.com/mndrix/function_expansion

Installation

Using SWI-Prolog 6.3 or later:

$ swipl
1 ?- pack_install(function_expansion).