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

## \+/1

#### Description

    \+ Goal

Not-provable meta-predicate. True iff `call(Goal)` is false. This built-in meta-predicate is declared as a private method and thus cannot be used as a message to an object.

#### Template and modes

    \+ +callable

#### Errors

Goal is a variable:
  `instantiation_error`
Goal is neither a variable nor a callable term:
  `type_error(callable, Goal)`

#### Examples

Not-provable goal in the context of the object or category containing the call:
  `\+ Goal`
Not-provable goal sent as a message to self:
  `\+ ::Goal`
Not-provable goal sent as a message to an explicit object:
  `\+ Object::Goal`

#### See also

`call/1-N`, `ignore/1`, `once/1`