The Equals and NotEqual operators
return true if both names refer to the same tile.
Equals can be abbreviated = and NotEqual can be abbreviated #.
Try the following on the All Here Revisited world:
Forall x (Square(x) and Large(x) -> x=a)
Exists y (Westof(y,a) and y=e)
Exists y (Samerow(y,c) and y#f)
Here is a way to test if at least one but not all
tiles have a given property, in this case the property
of being a square:
Exists x Square(x) and not Forall x Square(x)
It returns true on the world All Here and false on the
world Four Squares.
Precedence and Ambiguity
Index