Smalltalk - Re: how to model this a better way

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Re: how to model this a better way

Posted by Richard Sargent on Apr 18, 2019; 5:17pm
URL: https://forum.world.st/how-to-model-this-a-better-way-tp5098396p5098405.html

On Thu, Apr 18, 2019 at 10:01 AM Roelof Wobben <[hidden email]> wrote:

yep, I have read that one
but I never gets a answer how I can "convert" a point to something like north, east

because the challenge wants this to be the answer :

(Dictionary new
                add: 'direction' -> 'north';
                add:
                    'position'
                        ->
                            (Dictionary new
                                add: 'x' -> 0;
                                add: 'y' -> 0;
                                yourself);
                yourself)

If you have previously defined a "representation map", you would be golden.

e.g.

Dictionary new

at: self northDirectionVector put: 'north';

at: self eastDirectionVector put: 'east';

at: self southDirectionVector put: 'south';

at: self westDirectionVector put: 'west';

yourself.

Then:

(Dictionary new
add: 'direction' -> (self directionRepresentationMap at: self directionVector);

...

and I think I need then to use if then , which I try to avoid as much as possible.

Roelof

Op 18-4-2019 om 18:33 schreef Richard Sargent:

On Thu, Apr 18, 2019 at 8:57 AM Roelof Wobben <[hidden email]> wrote:

Hello,

I know I have asked earlier but im still stuck on this one : https://github.com/exercism/problem-specifications/blob/master/exercises/robot-simulator/description.md

I tried with all double dispatch but that will be a lot of duplicate classes

The problem I cannot solve right is that a robot can move or turn. when a robot turns only the direction the robot is facing changes and the position not. when a robot moves the facing direction stays the same but the position changes. but the change is dependend on the facing. Also the new facing direction is dependend on the old facing direction/

How can I model this the best.

I already have a object Robot that contains the facing direction and the current position

or tried without it but then I use a lot of if then's

so it there a better way to model this problem so it will be all nice and readable code.

If I remember correctly, Richard O'Keefe gave you a viable design. 1) Use a Point for your direction vector. 2) Use a second Point for your position.

e.g. if you align the compass with a Cartesian plane, 0@1 is North, 0@-1 is South, 1@0 is East, and -1@0 is West. When you move, you add the direction vector to your current position. If you allow movements of greater than a single unit, you multiply the direction vector by the distance before adding that product to the position.

Roelof