CurryInfo: base-3.4.0 / Control.Search.Unsafe.oneValue

 
oneValue :: a -> Maybe a
#ifdef __KICS2__
oneValue x =
  let vals = ST.allValuesWith ST.dfsStrategy (ST.someSearchTree x)
  in (if null vals then Nothing else Just (head vals))

 no demanded arguments

 deterministic operation

 
Returns just one value for an expression.
If the expression has no value, `Nothing` is returned.
Conceptually, the value is computed on a copy of the expression,
i.e., the evaluation of the expression does not share any results.
In PAKCS, the evaluation suspends as long as the expression
contains unbound variables or the computed
value contains unbound variables.

Note that this operation is not purely declarative since
the computed value depends on the ordering of the program rules.
Thus, this operation should be used only if the expression
has a single value.

 _

 referentially transparent operation

 no fixity defined

 {(_) |-> {Just,Nothing}}

 oneValue

 no precedence defined

 {Just,Nothing}

 a -> Prelude.Maybe a

 operation might suspend on free variables

 yes

 possibly non-reducible on same data term