###
Returns the real part of complex z
z real(z)
- -------
a + i b a
exp(i a) cos(a)
Eval_real = ->
push(cadr(p1))
Eval()
real()
real = ->
save()
rect()
p1 = pop()
push(p1)
conjugate()
add()
push_integer(2)
divide()
restore()