[Haskell-beginners] Function problem

[David McBride]

If you pass a program into this instruction, if it sees a shoot, it will
modify it slightly, if it is some other instruction, it will simply leave
the instruction unchanged, and then call itself on the rest of the
program.  Use pattern matching to do this (untested code):

adjust :: Direction -> Program -> Direction
adjust dir (Shoot point next) = Shoot (adjustPoint dir point) $ adjust dir
next
  where
    adjustPoint :: Dir -> Point -> Point
    adjustPoint N (x,y) = (x, y+1)
    adjustPoint ... = ...

adjust dir (Move d next) = Move d $ adjust dir next
adjust ... = ...
adjust _ (Surrender) = Surrender



On Mon, Jun 22, 2015 at 12:08 PM, Bruno Sotelo Klinec <
janus_1118 at outlook.com> wrote:

> Hi there! I was hoping you could help me a bit here with making a
> function. I am asked to write functions to make a mini robot game, which
> uses these data and types:
>
> data Program = Move Direction Program
>                 |Radar (Robot -> Point) Program
>                 |Shoot Point Program
>                 |Surrender
> data Direction = N|S|E|O
> type Point = (Int,Int)
> data Robot = R1|R2
>
> And then I have to write functions like this:
> prog1::Program
> prog1 = Move E $ Radar R1 (2,4) $ Radar R2 (5,6) $ Shoot (5,7) prog1
>
> My problem is the function adjust::Direction->Program->Program that takes
> one direction and a program and moves every shot in that program one unit
> in the given direction. I can't figure out how to do this, I would really
> appreciate you could help me, thanks!
>
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>
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