One of Each
One of Each only accepts strings that have one A and one B; that is, only AB and BA. Note how the top of this image is slightly defocused, which the feature extraction is robust to.
Annotated Image
Program Specification
;;;
;;; Preamble
;;;
(set-logic ALL)
;;;
;;; State Definitions
;;;
(define-fun is-state ((q Int)) Bool
(and (< (- 1) q) (< q 5)))
(define-fun is-accepting ((q Int)) Bool
(or (= q 3)))
(declare-fun IS () Int)
(assert (is-state IS))
(assert (not (= 0 IS)))
;;;
;;; Transition Definitions
;;;
(declare-fun T (Int String) Int)
;; All transitions must go to a valid state
(assert (forall ((q Int) (symb String))
(=> (is-state q) (is-state (T q symb)))))
;; It must not be possible to leave the zero state
(assert (forall ((symb String)) (= 0 (T 0 symb))))
;; Defined transitions
(assert (= 1 (T 2 "A")))
(assert (= 3 (T 1 "B")))
(assert (= 3 (T 4 "A")))
(assert (= 4 (T 2 "B")))
;; Negative transitions
(assert (forall ((symb String))
(=> (not (or (= symb "B")))
(= 0 (T 1 symb)))))
(assert (forall ((symb String))
(=> (not (or (= symb "A") (= symb "B")))
(= 0 (T 2 symb)))))
(assert (forall ((symb String))
(=> (not (or false))
(= 0 (T 3 symb)))))
(assert (forall ((symb String))
(=> (not (or (= symb "A")))
(= 0 (T 4 symb)))))
;;;
;;; Examples
;;;
(define-fun-rec exec-dfa ((q Int) (input String)) Bool
(ite (= 0 (str.len input))
(is-accepting q)
(exec-dfa (T q (str.at input 0)) (str.substr input 1 (- (str.len input) 1)))))
;; Positive
(assert (exec-dfa IS "AB"))
;; Negative
(assert (not (exec-dfa IS "BB")))
;;;
;;; Postamble
;;;
(check-sat)
(get-model)Synthesized Program
sat
(
(define-fun IS () Int
2)
(define-fun T ((x!0 Int) (x!1 String)) Int
(let ((a!1 (or (and (<= 1 x!0)
(<= 2 x!0)
(<= 3 x!0)
(not (<= 4 x!0))
(not (= x!1 "A"))
(not (= x!1 "B")))
(and (<= 1 x!0)
(<= 2 x!0)
(<= 3 x!0)
(not (<= 4 x!0))
(= x!1 "A")
(not (= x!1 "B")))
(and (<= 1 x!0)
(<= 2 x!0)
(<= 3 x!0)
(<= 4 x!0)
(not (= x!1 "A"))
(not (= x!1 "B")))
(and (<= 1 x!0)
(<= 2 x!0)
(not (<= 3 x!0))
(not (= x!1 "A"))
(not (= x!1 "B")))
(and (<= 1 x!0)
(not (<= 2 x!0))
(= x!1 "A")
(not (= x!1 "B")))
(and (not (<= 1 x!0)) (= x!1 "A") (not (= x!1 "B")))
(and (not (<= 1 x!0)) (= x!1 "B"))
(and (<= 1 x!0) (<= 2 x!0) (<= 3 x!0) (<= 4 x!0) (= x!1 "B"))
(and (<= 1 x!0)
(<= 2 x!0)
(<= 3 x!0)
(not (<= 4 x!0))
(= x!1 "B"))
(and (<= 1 x!0)
(not (<= 2 x!0))
(not (= x!1 "A"))
(not (= x!1 "B")))
(and (not (<= 1 x!0)) (not (= x!1 "A")) (not (= x!1 "B")))))
(a!2 (or (and (<= 1 x!0)
(<= 2 x!0)
(<= 3 x!0)
(<= 4 x!0)
(= x!1 "A")
(not (= x!1 "B")))
(and (<= 1 x!0) (not (<= 2 x!0)) (= x!1 "B"))))
(a!3 (ite (and (<= 1 x!0)
(<= 2 x!0)
(not (<= 3 x!0))
(= x!1 "A")
(not (= x!1 "B")))
1
7)))
(let ((a!4 (ite (and (<= 1 x!0) (<= 2 x!0) (not (<= 3 x!0)) (= x!1 "B"))
4
(ite a!2 3 a!3))))
(ite a!1 0 a!4))))
)