ometa M {
  fact 0                         -> 1,
  fact :n ?(n > 0) fact(n - 1):m -> (n * m)
}
M.match(5, "fact")

ometa G {
  //Constructors
  Edge :pa :pb ?(pa.isNumber && pb.isNumber) -> {a: pa, b: pb, isEdge: true }

  //There should be a Vert, or have Graph check for isnumber on each?

  //should check types more
  Graph :v :e ?(v.isSequenceable && e.isSequenceable) -> {verts: v, edges: e, isGraph: true},

  /*
  Cell :px :py :pz ?(px.isNumber && py.isNumber && pz.isNumber) -> {x: px, y: py, z: pz, isCell: true},
  Cell :px :py :pz ?((!px.isNumber && py.isNumber && pz.isNumber)) -> {x: px, y: py, z: pz, isCell: true},

  Euclidian Cell:a Cell:b -> (abs(a.x-b.x) + abs(a.y-b.y) + abs(a.z+b.z)),

  Neighbors Cell:a Cell:b Euclidian(a,b):e ?(e == 1) -> true
  Neighbors Cell:a Cell:b -> false,
  */

  Test :x ?(x==0) Graph([1,2,3],[{a: 1, b: 2}, {a: 1, b: 3}]):g -> g,
  //Test :x ?(x==1) Cell(1,1,1):c -> c,
  //Test :x ?(x==2) Cell(1,1,1):a Cell(1,1,2):b Euclidian(a,b):c -> c,
  Test :other -> other
}
console.log('compiled')
var r0 = G.match(0,'Test');
console.log(['Test0:',r0])
var r1 = G.match(1,'Test');
console.log(['Test1:',r1])
var r1 = G.match(2,'Test');
console.log(['Test2:',r1])