{ (x)       /[0]/[1][x]          | bool }
{ (x)       /[1]/[0][x]          | not  }
{ (x)(y)    /[0]/[y][x]          | and  }
{ (x)(y)    /[y]/[1][x]          | or   }
{ (x)(y)    /[y]/</[y][not]>[x]  | xor  }
{ (x)(y)    /</[y][not]>/[y][x]  | xnor }