Library with operations to encapsulate search, i.e., nondeterministic
computations. Note that some of these operations are not fully declarative,
i.e., the results depend on the order of evaluation and program rules.
There are newer and better approaches the encapsulate search,
in particular, set functions (see module Control.SetFunctions
in package setfunctions
), which should be used.
Author: Michael Hanus
Version: September 2023
getAllValues
:: a > IO [a]
Gets all values of an expression (similarly to Prolog's findall ).

getOneValue
:: a > IO (Maybe a)
Gets one value of an expression. 
getAllFailures
:: a > (a > Bool) > IO [a]
Returns a list of values that do not satisfy a given constraint. 
allValues
:: a > [a]
Returns all values of an expression. 
oneValue
:: a > Maybe a
Returns just one value for an expression. 
someValue
:: a > a
Returns some value for an expression. 
isFail
:: a > Bool
Does the computation of the argument to a headnormal form fail? Conceptually, the argument is evaluated on a copy, i.e., even if the computation does not fail, it has not been evaluated. 
rewriteAll
:: a > [a]
Gets all values computable by term rewriting. 
rewriteSome
:: a > Maybe a
Similarly to rewriteAll but returns only some value computable by term rewriting. 
Gets all values of an expression (similarly to Prolog's 
Gets one value of an expression. Returns 
Returns a list of values that do not satisfy a given constraint.

Returns all values of an expression. 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 ordering of the computed values depends on the ordering of the program rules.

Returns just one value for an expression.
If the expression has no value, 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.

Returns some value for an expression. If the expression has no value, the computation fails. 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. 
Does the computation of the argument to a headnormal form fail? Conceptually, the argument is evaluated on a copy, i.e., even if the computation does not fail, it has not been evaluated. 
Gets all values computable by term rewriting.
In contrast to

Similarly to rewriteAll
but returns only some value computable
by term rewriting. Returns
