Alert message does not display in while statement

[Adesu]

Hi Alls,
I have a simple code to check if a variable same as a target,then alert message would display,I just repeat test it,but always fail,any am I wrong?

(defun c:test (/ sdia hei)
  (setq sdia 25)
  (setq hei 21)
  (while
    (if
      (= hei (* sdia 0.8))
      (alert "\nTarget has finish")
      )                                              ; if
    (setq hei (- hei 0.1))
    )                                                ; while
  )                                                  ; defun

[ElpanovEvgeniy]

(defun c:test (/ sdia hei)
  (setq sdia 25)
  (setq hei 21)
  (while (if (equal hei (* sdia 0.8) 0.01)
           (alert "\nTarget has finish")
           (setq hei (- hei 0.1))
         ) ; if
  ) ; while
)

[CAB2k]

(defun c:test (/ sdia hei)
  (setq sdia 25)
  (setq hei 21)
  (while (> hei (* sdia 0.8))
    (setq hei (- hei 0.1))
  )
  (alert "\nTarget has finish")
)

[Adesu]

Hi elpanov,
It's great,many thanks for you.

(defun c:test (/ sdia hei)
  (setq sdia 25)
  (setq hei 21)
  (while (if (equal hei (* sdia 0.8) 0.01)
           (alert "\nTarget has finish")
           (setq hei (- hei 0.1))
         ) ; if
  ) ; while
)