# `retractall/1`

## Description

    retractall(Head)

Retracts all clauses with a matching head for an object dynamic predicate.

When the predicate indicator for `Head` is declared in a uses/2 or use_module/2 directive, the clauses are retracted in the referenced object or module. When the backend Prolog compiler supports a module system, the predicate argument can also be module qualified.

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

    retractall(@callable) - one

## 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 all clauses with a matching head of a dynamic predicate in this:
`retractall(Head)`
To retract all clauses with a matching head of a public or protected dynamic predicate in self:
`::retractall(Head)`
To retract all clauses with a matching head of a public dynamic predicate in an explicit object:
`Object::retractall(Head)`

See also

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