pattern-zebra

Graph-first constraint modeling. The property graph is the system of record; FlatZinc is a compilation target.

Constraint problems are written as .csp.gram files using Gram notation. Variables, domains, and constraints are graph nodes; relationships wire them together. The zebra CLI compiles a gram file to FlatZinc or solves it in-process using the Huub CP+SAT solver.

Install

cargo install zebra

To install from source:

cargo install --path crates/zebra

Usage

Given a .csp.gram file:

{kind: "csp", name: "two-integers"}

(x:Variable {name: "x"})  (dx:Domain {range: 1..3})
(y:Variable {name: "y"})  (dy:Domain {range: 1..3})
(c1:Constraint {kind: "int_lt"})

(x)-[:HAS_DOMAIN]->(dx)
(y)-[:HAS_DOMAIN]->(dy)
(c1)-[:ARG {pos: 0}]->(x)
(c1)-[:ARG {pos: 1}]->(y)

Solve (in-process, no external tools required):

zebra solve scenarios/two-integers/two-integers.csp.gram
# x = 2;
# y = 3;

Emit FlatZinc (for use with any FlatZinc-compatible solver):

zebra emit scenarios/two-integers/two-integers.csp.gram
# var 1..3: x;
# var 1..3: y;
# constraint int_lt(x, y);
# solve satisfy;

Graph schema

Node label	Key properties	Meaning
Variable	name	Decision variable
Domain	range	Variable domain (gram range, e.g. 1..10)
Constraint	kind	CP constraint atom (int_lt, int_eq, int_lin_eq, all_different)

Relationship	Properties	Meaning
HAS_DOMAIN	—	Binds a variable to its domain
ARG	pos	Positional argument to a constraint