Week 9: Project 1

In this post, I am going to talk about the things I have learnt and problems that I encountered in the Project 1. Before I started working on this project, I was not that familiar with the codes; however, this project indeed helped me on giving me a better insight of different functions.

1. About "make-color"

(define (clarify-color c)

  (make-color
   (color-red c)
   (color-green c)
   (color-blue c)
   (cond
     [(> (+ (color-red c) (color-green c) (color-blue c)) 650) 0]
     [else (color-alpha c)])))

I have to make a "check-expect" basing on the above,
at first I tried putting the entire function "(make-color 1 2 3 0)" to c.
However, this can actually be done very easily.

(check-expect (clarify-color (make-color 0 0 255 0))
               (make-color
                0
                0
                255
                0
                ))

2.  Clarify-image

I got stuck for more than 4 hours on fixing the function "clarify-image".
After looking back and working on the previous exercise "map and map-image", I got this function working finally!

An example from the exercise "mapping",

(map-image less-green "pic: hacker")

To define a function by using another function, which is the "clarify-color", I had to use the "map-image".
Here is what I did at last,

(define (clarify-image im) (map-image clarify-color im))

3.  Set-clock

After fixing the function "set-clock",

(define (set-clock h m s s/g) (make-clocktime h m s s/g))

I had to make two "check-expect" for the function.
It might somehow seem easy for the others after they've looked at your work;
however, to have every next function working fine, you always have to trace back and truly understand every steps.

Without studying the above functions, you might not know h=hours, m=minutes, s=seconds, s/g=STOP/GO;
and you as well might not know what "make-clocktime" is.
This is one of the check expect,

(check-expect (set-clock 6 7 8 STOP) (make-clocktime 6 7 8 STOP))

4. check-key

I had to fix the function "check-key" by following the hints from the "check-expect".
I had spent quite a while on this as I was so confused about what to do with the last section "s/g".

But at last, I found that it could actually be done very simply, it's just that I had been thinking in a too complicated way.

(check-expect (check-key (make-clocktime 1 2 3 GO) "down") (make-clocktime 1 2 3 STOP))

(define (check-key c k)
  (cond
    [(equal? k "down")
     (make-clocktime
   (clocktime-hours c)
   (clocktime-minutes c)
   (clocktime-seconds c)
   STOP)]
    [else c]))

To sum up, I think I have learnt a lot after doing the project. It is just kind of like a revision, helping clarifying everything we have been learning.