Logtalk reference manual
Built-in method: retract/1
Contents > Reference Manual > Built-in Methods > retract/1

## retract/1

#### Description

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

Retracts a clause for a dynamic predicate. 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. Otherwise the clause is retracted in an object's dynamic predicate. On backtracking, the predicate retracts the next matching clause.

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.

#### Template and modes

    retract(+clause)

#### 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 local dynamic predicate or 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`