#!/usr/bin/gcl -f

(defun read-int (text)
    (format t text)
    (read)
)

(defun print-result ( a b c x)
    (let
        (
            (bSign (if (< b 0) "" "+"))
            (cSign (if (< c 0) "" "+"))
        )
        (format t
            "For ~A*x^2 ~A ~A*x ~A ~A = 0 You can find ~A.~%"
            a
            bSign b
            cSign c
            x
        )
    )
)

(defun calc-double-x (a b d)
    (list
        ( / (+ b (sqrt d)) (* 2 a))
        ( / (- b (sqrt d)) (* 2 a))
    )
)

(defun calc-single-x (a b)
    (list
        (/ (- b) (* 2 a))
    )
)

(defun calc-x (a b c)
    (let
        (
            (d (- (* b b) (* 4 a c)))
            (x 0)
        )
        (if (> d 0)
            (calc-double-x a b d)
            (if (eql d 0)
                (calc-single-x a b)
                nil
            )
        )
    )
)

(defun square ()
    (format t "a*x^2 + b*x + c = 0~%")

    (let
        (
            (a (read-int "a="))
            (b (read-int "b="))
            (c (read-int "c="))
        )
        (print-result a b c (calc-x a b c))
    )
)


(square)
(bye)