object
optional
¶
Constructors for optional terms. An optional term is either empty or holds a value. Optional terms should be regarded as opaque terms and always used with the optional/1
object by passing the optional term as a parameter.
static, context_switching_calls
Type-checking support: This object also defines a type
optional
for use with thetype
library object.
Public predicates¶
empty/1
¶
Constructs an empty optional term.
static
empty(Optional)
empty(--nonvar)
- one
of/2
¶
Constructs an optional term holding the given value.
static
of(Value,Optional)
of(@term,--nonvar)
- one
from_goal/3
¶
Constructs an optional term holding a value bound by calling the given goal. Returns an empty optional term if the goal fails or throws an error.
static
from_goal(Goal,Value,Optional)
from_goal(0,*,*)
from_goal(+callable,--term,--nonvar)
- one
from_goal/2
¶
Constructs an optional term holding a value bound by calling the given closure. Returns an empty optional term if the closure fails or throws an error.
static
from_goal(Closure,Optional)
from_goal(1,*)
from_goal(+callable,--nonvar)
- one
Protected predicates¶
(no local declarations; see entity ancestors if any)
Private predicates¶
(no local declarations; see entity ancestors if any)