Module proto_vulcan::relation[−][src]

Expand description

Relations

Proto-vulcan relations are implemented as Rust-functions that have LTerm-type parameters, and Goal return value. Because proto-vulcan is parametrized by generic User-type, functions must be made generic with respect to it if we want to use anything other than the default DefaultUser. A simple function example that implements a relation that succeeds when argument s is an empty list is declared as:

extern crate proto_vulcan;
use proto_vulcan::prelude::*;

pub fn emptyo<U: User, E: Engine<U>>(s: LTerm<U, E>) -> Goal<U, E> {
    proto_vulcan!([] == s)
}

Recursion

The relation-constructor calls within proto_vulcan!-macro are evaluated immediately when the relation-constructor containing the macro is called; relations within proto-vulcan! are just function calls. Recursive relations must instead use proto_vulcan_closure!-macro, that puts the function calls and necessary context into a closure that will be evaluated later.

extern crate proto_vulcan;
use proto_vulcan::prelude::*;

pub fn append<U: User, E: Engine<U>>(l: LTerm<U, E>, s: LTerm<U, E>, ls: LTerm<U, E>) -> Goal<U, E> {
    proto_vulcan_closure!(
       match [l, s, ls] {
           [[], x, x] => ,
           [[x | l1], l2, [x | l3]] => append(l1, l2, l3),
       }
    )
}

Modules

clpfd

CLP(FD)

Functions

always

A relation that succeeds an unbounded number of times.

append

A relation where l, s, and ls are proper lists, such that ls is s appended to l.

cons

A relation such that the out parameter is equal to rest parameter appended to first parameter. The first parameter is the head of the list out and the rest is the tail.

diseq

Disequality relation.

diseqfd

Disequality relation for finite domains.

distinct

A relation which guarantees that all elements of l are distinct from each other.

distinctfd

empty

A relation that succeeds when s is an empty list. This is equivalent to s == [].

eq

Equality relation.

fail