The constraint a group carries: every value in it equals what the pin says.
A term pin is the value. A triple pin is a shape - the value is a triple term, and each of its
three positions is a group in its own right - so it fixes a value only once all three are decided, and
constrains it partially until then. Holding group ids rather than terms is what makes a position nobody
named an anonymous group: it unifies and carries a pin and a range like any other, while contributing
nothing to the members of the set.
The constraint a group carries: every value in it equals what the pin says.
A
termpin is the value. Atriplepin is a shape - the value is a triple term, and each of its three positions is a group in its own right - so it fixes a value only once all three are decided, and constrains it partially until then. Holding group ids rather than terms is what makes a position nobody named an anonymous group: it unifies and carries a pin and a range like any other, while contributing nothing to the members of the set.