ConstraintStore

Inherits from: Object

A monotonic shared constraint store for concurrent constraint programming.

ConstraintStore holds a single CUE value that starts as top (unconstrained) and monotonically narrows via unification. Processes tell constraints to add information and ask constraints to check entailment, blocking until the store implies their query.

Test

store := ConstraintStore new.
store isConsistent >>> true

Test

store := ConstraintStore new.
ctx := CueContext new.
constraint := (ctx compileString: '{x: 42}') value.
(store tell: constraint) isSuccess >>> true
store tryAsk: constraint >>> true

Test

store := ConstraintStore new.
ctx := CueContext new.
store tell: (ctx compileString: '{x: 42}') value.
store tell: (ctx compileString: '{y: "hello"}') value.
query := (ctx compileString: '{x: int, y: string}') value.
store tryAsk: query >>> true

Test

store := ConstraintStore new.
ctx := CueContext new.
c1 := (ctx compileString: '{x: 42}') value.
store tell: c1.
c2 := (ctx compileString: '{x: "hello"}') value.
(store tell: c2) isSuccess >>> false
store isConsistent >>> true

Test

store := ConstraintStore new.
ctx := CueContext new.
query := (ctx compileString: '{x: int}') value.
store tryAsk: query >>> false

Test

store := ConstraintStore new.
ctx := CueContext new.
store tell: (ctx compileString: '{x: 42}') value.
val := store value.
(val lookup: 'x') value toMaggie value >>> 42

Class Methods

primitives

class new

Instance Methods

primitives

primAsk:

primIsConsistent

primPrintString

primTell:

primTryAsk:

primValue

primWatch:do:

uncategorized

ask:

Block until the store subsumes (entails) the given CUE constraint. Returns true when the query is entailed.

The argument must be a CueValue.

askString:

Convenience: blocking ask using a CUE source string. Returns true when entailed.

isConsistent

Return true if the store is consistent (not bottom).

printString

Return a human-readable description.

tell:

Tell a CUE constraint to the store (monotonic narrowing via unification). Returns a Success Result if the constraint is consistent with the store, or a Failure Result if it conflicts (store unchanged on failure).

The argument must be a CueValue.

tellString:

Convenience: tell a CUE source string (compiles it first). Returns a Result.

tryAsk:

Non-blocking entailment check. Returns true if the store currently subsumes the query, false otherwise.

The argument must be a CueValue.

tryAskString:

Convenience: non-blocking ask using a CUE source string. Returns true/false.

value

Return the current store state as a CueValue (snapshot).

watch:do:

Register a block callback that fires when a constraint becomes entailed. If the constraint is already entailed, the block is invoked immediately. Otherwise, a goroutine waits and invokes the block when a future tell makes it entailed.