id = 174
number = 80
visible = False
facts = 'denotational_semantics_aux__predicates'

solution = '''\
prog_listswap(In-->Out) -->
    [begin], instructs174((In,1)-->(Out,_)), [end].

instructs174((R0,C0)-->(R,C)) -->
    instr174((R0,C0)-->(R,C)).
instructs174((R0,C0)-->(R,C)) -->
    instr174((R0,C0)-->(R1,C1)),
    instructs174((R1,C1)-->(R,C)).

instr174((R0,C0)-->(R0,C)) -->
    [left], { C0 > 1, C is C0 - 1 ; C0 =< 1, C is C0 }.
instr174((R0,C0)-->(R0,C)) -->
  [right], { length(R0, LenR0),
            ( C0 < LenR0, C is C0 + 1 ; C0 >= LenR0, C is C0 ) }.

instr174((R0,C0)-->(R,C0)) -->
  [swap], {swap(R0,C0,R)}.'''