# retract/1

## Description

    retract(Head)
    retract((Head:-Body))

Retracts a clause for an object dynamic predicate. On backtracking, the predicate retracts the next matching clause.

When the predicate indicator for `Head` is declared in a uses/2 or use_module/2 directive, the clause is retracted in the referenced object or module.

This method may be used to retract clauses for predicates that are not declared dynamic for dynamic objects provided that the predicates are declared in this.

## Modes and number of proofs

    retract(+clause) - zero_or_more

## Errors

Head is a variable:
`instantiation_error`
Head is neither a variable nor a callable term:
`type_error(callable, Head)`
The predicate indicator of Head, Name/Arity, is that of a private predicate:
`permission_error(modify, private_predicate, Name/Arity)`
The predicate indicator of Head, Name/Arity, is that of a protected predicate:
`permission_error(modify, protected_predicate, Name/Arity)`
The predicate indicator of Head, Name/Arity, is that of a static predicate:
`permission_error(modify, static_predicate, Name/Arity)`
The predicate indicator of Head, Name/Arity, is not declared:
`existence_error(predicate_declaration, Name/Arity)`

## Examples

To retract a matching clause of a dynamic predicate in this:
`retract(Clause)`
To retract a matching clause of a public or protected dynamic predicate in self:
`::retract(Clause)`
To retract a matching clause of a public dynamic predicate in an explicit object:
`Object::retract(Clause)`

See also

abolish/1, asserta/1, assertz/1, clause/2, retractall/1, dynamic/0, dynamic/1, uses/2, use_module/2