| definition: |
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)) |
| demand: |
no demanded arguments |
| deterministic: |
deterministic operation |
| documentation: |
--- 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. |
| failfree: |
_ |
| indeterministic: |
referentially transparent operation |
| infix: |
no fixity defined |
| iotype: |
{(_) |-> {Just,Nothing}}
|
| name: |
oneValue |
| precedence: |
no precedence defined |
| result-values: |
{Just,Nothing}
|
| signature: |
a -> Prelude.Maybe a |
| solution-complete: |
operation might suspend on free variables |
| terminating: |
yes |
| totally-defined: |
possibly non-reducible on same data term |