An assortment of questions.

Ignatz

Yes it is, but it is used to turn on an indicator, which is what decides if the ellipse is drawn

RonJeffries

ISTM that ElapsedTime == 1 will occur at most once.

Ignatz

It will probably not occur at all because the interval between drawing is not exactly 1/60 second, so instead of 1 you will get 1.000329 or something like it.

RonJeffries

right, thus "at most once"

dave1707

@RonJeffries Actually, the ellipse would be drawn constantly. As ElapsedTime increases and is equal to 1, doStuff increments to 1. If doStuff is 1, the ellipse is drawn. As ElapsedTime increases, it will never be equal to 1 again, so doStuff will never increase and will stay at 1, which will continue to draw the ellipse. But this is assuming that ElapsedTime will equal 1 as it increases.

Ignatz

ElapsedTime won't ever exactly equal 1, that's why I used a > test.

dave1707

@Ignatz I was going by the way the code was originally written and assuming that ElapsedTime would equal 1. Then the ellipse would be drawn from that point forward. I'm sure if that code was run enough times, ElapsedTime would equal 1 at least once, but I'm not going to try and verify that.

Ignatz

I don't know how many times I need to say this.

ElapsedTime is NEVER likely to equal 1.

Just run this code. It will print a message if ElapsedTime is ever an integer, not just 1, but 2,3,4,...

Don't hold your breath waiting...

function setup()
    parameter.text("Time","")
end

function draw()
    if ElapsedTime==math.floor(ElapsedTime) then 
        print("success after "..ElapsedTime.." seconds") 
    end
    Time=math.floor(ElapsedTime)
end

dave1707

@Ignatz If something can happen, given enough time, it will. If your code ran long enough, or was restarted enough times, it will print success after some integer at least once. I'm not saying it would happen in my lifetime or yours or anyone's, but it would happen. If you take a zillion coins and throw them in the air enough times, they'll all land on heads or tails at least once. If you can create a truely random number, then every number, no matter how large or small, has the same chance of be chosen.

Ignatz

Yes, but he wanted something to happen when the program had been running 1 second - not just once in a bajillion times, but every time the program runs.

dave1707

@Ignatz That was a good example of, the code doesn't give you what you want, even though it looks correct. Anyways, math on computers isn't exact and you need to code for that.

dave1707

We have == for equal, ~= for not equal, <= for less than or equal, and >= for greater than or equal. What we need is ?= for about equal. This would compare 2 numbers and be true if the numbers were within some limit of each other. The aboutEqual function in the code below shows how the program being discussed would run. I have the limit set to .01, so if ElapsedTime is within +/- .01 of 1, then the ellipse will be drawn. Or, the aboutEqual function could just be used instead of waiting for ?= .

function setup()
    dostuff=0
end

function draw()
    background(255, 255, 255, 255)
    if aboutEqual(ElapsedTime,1,.01) then
        dostuff=dostuff+1
    end
    strokeWidth(5)
    fill(0)
    if dostuff == 1 then
        ellipse(100,100,100)
    end
end

function aboutEqual(v1,v2,limit)
    if math.abs(v1-v2) < limit then
        return true
    end
    return false
end

Ignatz

Yes, you would think that Simeon, living in Australia, would have included a function based on the Aussie maxim "near enough is good enough"

MattthewLXXIII

Hi again,
I've just started to play around with physics bodies.

-- Bouncy thing
function setup()
    bodies={}
    box=physics.body(CHAIN,vec2(0,HEIGHT),vec2(0,0),vec2(WIDTH,0),vec2(WIDTH,HEIGHT),vec2(0,HEIGHT))
    ball=physics.body(CIRCLE,50)
    ball.x=WIDTH/2
    ball.y=HEIGHT/2
    ball.restitution=0.5
    ball.gravityScale=0
    ball.type=DYNAMIC
    ball.bullet=true
    ball.interpolate=true
    ball.positions={}
    ball.positions[1]=ball.position
    ball.positions[2]=ball.position
    i=1
    player=physics.body(CIRCLE,50)
    player.type=STATIC
    table.insert(bodies,box)
    table.insert(bodies,ball)
    table.insert(bodies,player)
end
function draw()
    background(0)
    for k,v in pairs(bodies) do
        drawBody(v)
    end
    ball.positions[i]=ball.position
    ball.linearVelocity=(ball.positions[i]-ball.positions[3-i])*0.99/DeltaTime
    i=3-i
end
function touched(t)
    player.x=t.x
    player.y=t.y
end
function drawBody(body)
    pushStyle()
    pushMatrix()
    noFill()
    strokeWidth(5)
    stroke(255)
    translate(body.x, body.y)
    rotate(body.angle)
    if body.shapeType == POLYGON then
        local points = body.points
        for j = 1,#points do
            a = points[j]
            b = points[(j % #points)+1]
            line(a.x, a.y, b.x, b.y)
        end
    elseif body.shapeType == CHAIN or body.shapeType == EDGE then
        local points = body.points
        for j = 1,#points-1 do
            a = points[j]
            b = points[j+1]
            line(a.x, a.y, b.x, b.y)
        end
    elseif body.shapeType == CIRCLE then
--        line(0,0,body.radius-strokeWidth(),0)
        ellipse(0,0,body.radius*2)
    end
    popMatrix()
    popStyle()
end

EDIT: the problem seems to not be there any more. Is there a more elegant way to do the sliding? What are the drawbacks of setting bullet to true?