File: parity.ella

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TYPE bit = NEW(t | f).

FN PARITY_SPEC = (bit: in) -> bit:
 BEGIN SEQ
    STATE VAR parity INIT t;
    CASE in
    OF t: op := f,
       f: op := t
    ESAC;
    OUTPUT parity
END.

FN NOT = (bit: in) -> bit:
 CASE in
 OF f: t,
    t: f
 ESAC.

FN MUX = (bit: cntl in1 in2) -> bit:
 CASE cntl
 OF t: in1,
    f: in2
 ESAC.

FN REG = (bit) -> bit: DELAY(f, 1).

FN PARITY_IMP = (bit: in) -> bit:
BEGIN
   MAKE NOT: l1,
        MUX: l3 out,
        REG: l2 l5.
   JOIN (in,l1,l2) -> l3,
        t            -> l5,
        (l5, l3, l4) -> out,
        out          -> l2,
        l2           -> l1.
OUTPUT out
END.