reserve m,n for Nat,
  a for Int_position,
  i,j for Instruction of SCMPDS,
  s,s1,s2 for State of SCMPDS,
  k1 for Integer,
  loc for Nat,
  I,J,K for Program of SCMPDS;
reserve P,P1,P2 for Instruction-Sequence of SCMPDS;

theorem
  for s being 0-started State of SCMPDS,I,J being halt-free shiftable
  parahalting Program of SCMPDS,a being Int_position,k1 being Integer holds IC
  IExec(if>0(a,k1,I,J),P,s) = card I + card J + 2
proof
  let s be 0-started State of SCMPDS,
      I,J be halt-free shiftable parahalting Program of SCMPDS,
      a be Int_position,k1 be Integer;
  set IF=if>0(a,k1,I,J);
A1: I is_closed_on s,P & I is_halting_on s,P by Th11,Th12;
A2: J is_closed_on s,P & J is_halting_on s,P by Th11,Th12;
  per cases;
  suppose
    s.DataLoc(s.a,k1) > 0;
    then IExec(IF,P,s) = IExec(I,P,s) +* Start-At((card I+card J+2),SCMPDS)
    by A1,Th61;
    hence thesis by FUNCT_4:113;
  end;
  suppose
    s.DataLoc(s.a,k1) <= 0;
    then IExec(IF,P,s) = IExec(J,P,s) +* Start-At((card I+card J+2),SCMPDS)
    by A2,Th62;
    hence thesis by FUNCT_4:113;
  end;
end;
