The Links Programming Language
type t =
| UnboundColumns of Alias.Set.t(*

The columns could not be found in the lens sort.

| DefiningFDNotFound of Alias.Set.t(*

A functional dependency X -> Y with Y = drop could not be found.

| DropNotDefinedByKey(*

A functional dependency could not be found which defines the columns to be dropped by the key.

| DefaultDropMismatch(*

The number of columns to drop does not match the number of default values specified.

| DefaultDoesntMatchPredicate(*

The default value a for A does not satisfy PA.

| NotIndependent of Alias.Set.t(*

It is not possible to tell that P = PA join PU-A.

val equal : t -> t -> bool