
theorem
  xor2.<*0,0*>=0 & xor2.<*0,1*>=1 & xor2.<*1,0*>=1 & xor2.<*1,1*>=0 &
  xor2a.<*0,0*>=1 & xor2a.<*0,1*>=0 & xor2a.<*1,0*>=0 & xor2a.<*1,1*>=1
proof
  thus xor2.<*0,0*> = FALSE 'xor' FALSE by FACIRC_1:def 4
    .= 0;
  thus xor2.<*0,1*> = FALSE 'xor' TRUE by FACIRC_1:def 4
    .= 1;
  thus xor2.<*1,0*> = TRUE 'xor' FALSE by FACIRC_1:def 4
    .= 1;
  thus xor2.<*1,1*> = TRUE 'xor' TRUE by FACIRC_1:def 4
    .= 0;
  thus xor2a.<*0,0*> = 'not' FALSE 'xor' FALSE by Def7
    .= 1;
  thus xor2a.<*0,1*> = 'not' FALSE 'xor' TRUE by Def7
    .= 0;
  thus xor2a.<*1,0*> = 'not' TRUE 'xor' FALSE by Def7
    .= 0;
  thus xor2a.<*1,1*> = 'not' TRUE 'xor' TRUE by Def7
    .= 1;
end;
