Trying to port Snake game to 0.12, kind of confused

mike1127 · June 30, 2018, 8:04am

I’m trying to learn PureScript and mostly sticking to 0.12 although may be a mistake given that so few examples out there are compatible with it. I thought I would try to port the Snake game to 0.12, found here in its original version:

github.com

holdenlee/purescript-games/blob/master/src/Snake.purs?utf8=✓

module Snake where

import Prelude -- must be explicitly imported
import Control.Monad.Eff (Eff)
import Control.Monad.Eff.Console (CONSOLE, log)
import Control.Monad.Eff.Random (RANDOM, randomInt)
import Data.Array (length, uncons, slice, (:), last)
import Data.Array.Partial (head)
import Data.Functor
import Data.Generic
import Data.Int
import Data.Maybe
import Data.Traversable
import Data.Tuple
import Graphics.Canvas (CANVAS, closePath, lineTo, moveTo, fillPath,
                        setFillStyle, arc, rect, getContext2D,
                        getCanvasElementById, Context2D, Rectangle)
import Partial.Unsafe (unsafePartial)
import Signal (Signal, runSignal, foldp, sampleOn, map4)
import Signal.DOM (keyPressed)

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I created a file with lots of stub functions using unsafeCrashWith just to see if I could get the thing to type check. It’s having trouble which I don’t understand, something about record types not matching. Here is the file I created so far:

https://bitbucket.org/mike1127/snakeport/src/master/Main.purs

mike1127 · June 30, 2018, 8:05am

sorry, I see that my attempt to post unformatted code didn’t work. I’ll try another way – give me a few minutes. update: okay see post above with link to bitbucket

chexxor · June 30, 2018, 6:10pm

@mike1127 - I get “Access Denied” when trying to view that link to https://bitbucket.org/mike1127/snakeport/src/master/Main.purs

mike1127 · June 30, 2018, 8:15pm

Hi, I think it should be fixed. I set the repository to public. Also try

https://bitbucket.org/mike1127/snakeport/src/master/

if my first link doesn’t work.

Mike

chexxor · June 30, 2018, 9:58pm

A few of your functions have Partial => constraint. You’ll need to eject that at some point using unsafePartial. I can’t clone your project at this time to try building it, but that’s the first thing I saw. I’ll try cloning later.

chexxor · July 1, 2018, 2:47am

I managed to get it compiling again:

LMK if you have questions. I don’t know why Gen was the result of the step function – I can’t think of a reason to do that. Quickcheck is for tests, not for the main program.

mike1127 · July 1, 2018, 3:00am

Thanks! I was just copying code from a web page I found online which claimed to have a working port of the Elm “snake game” to Purescript. I think there were using Quickcheck as a pseudorandom generator for some aspect of the game. At this point I doubt their code was working. I’m going to continue working with it function-by-function, first to get it to compile, then to get it to run.