# 'for' function

###
x=0
y=2
for(do(x=sqrt(2+x),y=2*y/x),k,1,9)
float(y)

X: k
B: 1...9

1st parameter is the body
2nd parameter is the variable to loop with
3rd and 4th are the limits


###

#define A p3
#define B p4
#define I p5
#define X p6

Eval_for = ->
  i = 0
  j = 0
  k = 0

  loopingVariable = caddr(p1)
  if (!issymbol(loopingVariable))
    stop("for: 2nd arg should be the variable to loop over")

  push(cadddr(p1))
  Eval()
  j = pop_integer()
  if (isNaN(j))
    push p1
    return

  push(caddddr(p1))
  Eval()
  k = pop_integer()
  if (isNaN(k))
    push p1
    return


  # remember contents of the index
  # variable so we can put it back after the loop
  p4 = get_binding(loopingVariable)

  for i in [j..k]
    push_integer(i)
    p5 = pop()
    set_binding(loopingVariable, p5)
    push(cadr(p1))
    Eval()
    pop()

  # put back the index variable to original content
  set_binding(loopingVariable, p4)

  # return value

  push_symbol(NIL)