Datalog language preview

1. Transitive closure

Souffle directives, a fact, and a recursive rule

horizon-dark

// transitive closure over an edge relation
.decl edge(x: symbol, y: symbol)
.decl path(x: symbol, y: symbol)
.input edge
edge("a", "b").
edge("b", "c").

path(x, y) :- edge(x, y).
path(x, y) :- path(x, z), edge(z, y), !edge(y, x).

.output path

atom-one-dark

// transitive closure over an edge relation
.decl edge(x: symbol, y: symbol)
.decl path(x: symbol, y: symbol)
.input edge
edge("a", "b").
edge("b", "c").

path(x, y) :- edge(x, y).
path(x, y) :- path(x, z), edge(z, y), !edge(y, x).

.output path

github-dark

// transitive closure over an edge relation
.decl edge(x: symbol, y: symbol)
.decl path(x: symbol, y: symbol)
.input edge
edge("a", "b").
edge("b", "c").

path(x, y) :- edge(x, y).
path(x, y) :- path(x, z), edge(z, y), !edge(y, x).

.output path

dracula

// transitive closure over an edge relation
.decl edge(x: symbol, y: symbol)
.decl path(x: symbol, y: symbol)
.input edge
edge("a", "b").
edge("b", "c").

path(x, y) :- edge(x, y).
path(x, y) :- path(x, z), edge(z, y), !edge(y, x).

.output path

nord

// transitive closure over an edge relation
.decl edge(x: symbol, y: symbol)
.decl path(x: symbol, y: symbol)
.input edge
edge("a", "b").
edge("b", "c").

path(x, y) :- edge(x, y).
path(x, y) :- path(x, z), edge(z, y), !edge(y, x).

.output path

github

// transitive closure over an edge relation
.decl edge(x: symbol, y: symbol)
.decl path(x: symbol, y: symbol)
.input edge
edge("a", "b").
edge("b", "c").

path(x, y) :- edge(x, y).
path(x, y) :- path(x, z), edge(z, y), !edge(y, x).

.output path

2. Type declarations

.type and .functor directives

horizon-dark

.type Name <: symbol
.decl person(name: Name, age: number)
.functor double(x: number): number

person("Ada", 30).
person("Grace", 40).

atom-one-dark

.type Name <: symbol
.decl person(name: Name, age: number)
.functor double(x: number): number

person("Ada", 30).
person("Grace", 40).

github-dark

.type Name <: symbol
.decl person(name: Name, age: number)
.functor double(x: number): number

person("Ada", 30).
person("Grace", 40).

dracula

.type Name <: symbol
.decl person(name: Name, age: number)
.functor double(x: number): number

person("Ada", 30).
person("Grace", 40).

nord

.type Name <: symbol
.decl person(name: Name, age: number)
.functor double(x: number): number

person("Ada", 30).
person("Grace", 40).

github

.type Name <: symbol
.decl person(name: Name, age: number)
.functor double(x: number): number

person("Ada", 30).
person("Grace", 40).

3. Query with negation

a classic ?- query and negated subgoal

horizon-dark

?- path(X, "c"), !edge(X, "c").

atom-one-dark

?- path(X, "c"), !edge(X, "c").

github-dark

?- path(X, "c"), !edge(X, "c").

dracula

?- path(X, "c"), !edge(X, "c").

nord

?- path(X, "c"), !edge(X, "c").

github

?- path(X, "c"), !edge(X, "c").