h` computed the fixed point. In the schema here, `h1` had better be a
function which, when you give it suitable arguments, computes the
first fixed point `X1` (likewise for `h2` wrt the second fixed point
h` computed the fixed point. In the schema here, `h1` had better be a
function which, when you give it suitable arguments, computes the
first fixed point `X1` (likewise for `h2` wrt the second fixed point