Jumping with a rectangle

[iPoisonxL]

Hello! Just a quick question, how do I eliminate the tiniest bit of lag I get when I have a rectangle jump and land?

To clarify:

Here's some code

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if(self.y>=400-self.h)then --if y is greater than the ground height
        self.yvel = 0
        self.y = 400 - self.h
        self.onGround = true
    else
        self.y = self.y + (self.yvel * dt)
        self.yvel = self.yvel + 9.8
    end

When the player lands on the ground, he goes through the ground for 1 frame exactly. This happens because he would be, say, 1 pixel from the ground when he is moving let's say 2 pixels a frame. So he goes 1 pixel past the ground for 1 frame then gets rectified because of the line that says "self.y = 400 - self.h". How do I get rid of him going through the ground for a frame?

[Azhukar]

By adding velocity to the check.

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if(self.y+self.yvel>=400-self.h)then

[iPoisonxL]

By adding velocity to the check.

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if(self.y+self.yvel>=400-self.h)then

It just does this...

[Azhukar]

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if(self.y+self.yvel*dt>=400-self.h)then

Forgot * dt

[iPoisonxL]

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if(self.y+self.yvel*dt>=400-self.h)then

Forgot * dt

Thank you!! I don't think my brain is working too well I've been doing too much Haskell.

myBrain :: Haskell -> Lua

exception: cannot get type Haskell and return Lua

[kikito]

I think Lua and Haskell are like two extremes of the spectrum in programming. Lua is small and "loose", while Haskell is big and "correct".

I tried Haskell once, but was a bit exhausted after a while. I'm guessing it gets easier after you climb the initial learning curve, but I gave up before. What are you using / have you used to go over that curve?

Also, I will take this opportunity to plug my library, bump, here. It seems to do exactly what you are doing manually, in a generalized way (it calculates the point where the rectangle will impact and returns it to you).

[Azhukar]

I think functional programming is a waste of effort.

[kikito]

Well, even John Carmack needed years to warm up to it, and he's a genius, so I don't expect everyone to suddenly accept it . Nevertheless, try to keep an open mind towards it; it has some very valid merits.

[iPoisonxL]

I'm using http://learnyouahaskell.com, kikito. It's a very good guide but I've had to go to the IRC chat twice so far to get some basic understanding on function currying (all functions take one parameter, but return a function that take another etc) and other stuff that is totally off for programming paradigms. But I feel haskell is very, very powerful, and definitely not a waste of time cause of the whole lazy thing which lets you operate on INFINITE lists, without having a stack overflow or performance issues. And you can make code that looks really cool like this for example:

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 (<!!) :: (Eq a) => a -> [a] -> Bool
    _  <!! []  = False
    x <!! (l:ls) =
        if l == x then True else x <!! ls

or this:

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sumOddSquaresUnder :: Integer -> Integer
sumOddSquaresUnder n = sum . takeWhile (<n) . filter odd . map (^2) $ [1..]

Woohoo for Haskell

Note, I'm only like halfway done all the tutorials, I've still got a bit to do