Recursion does not work, stack problem?

General
1

Hi

I habe a problem with recursion in codea. The problem is that local variables in a function are change from an other function!! In other languages this does not happen.

Please see my example program. You can see that a variable “localvar” is changes from a recursive call!!
What can i do make this not happen?

Regards
Franz

Here is the code:

-- recusion test
iter=0

-- Use this function to perform your initial setup
function setup()
    print("Hello World!")
end

function recursion(n)
    
    localvar=n
    iter = iter + 1
    if iter>1 then
        print("i am in recursion")
    else
        print("iter ",iter)
        print("localvar ",localvar)
        copy=localvar
        recursion(2)
        print("localvar ",localvar)
        if copy~=localvar then print("this is a problem! this should not happen!") end
    end
    
end

-- This function gets called once every frame
function draw()
    -- This sets a dark background color 
    background(40, 40, 50)

    -- This sets the line thickness
    strokeWidth(5)
    print("start test")
    recursion(1)
    print("end test")
    -- Do your drawing here
    
end
2

Sorry i was too stupid to post the code, here is the correct version


-- recusion test
iter=0

-- Use this function to perform your initial setup
function setup()
    print("Hello World!")
end

function recursion(n)
    
    localvar=n
    iter = iter + 1
    if iter>1 then
        print("i am in recursion")
    else
        print("iter ",iter)
        print("localvar ",localvar)
        copy=localvar
        recursion(2)
        print("localvar ",localvar)
        if copy~=localvar then print("this is a problem! this should not happen!") end
    end
    
end

-- This function gets called once every frame
function draw()
    -- This sets a dark background color 
    background(40, 40, 50)

    -- This sets the line thickness
    strokeWidth(5)
    print("start test")
    recursion(1)
    print("end test")
    -- Do your drawing here
    
end
3

Recursion does work, the issue is that all variables are global unless you declare them as local. So adding a local in front of copy and localvar make the recursion work… except… you are using the global iter to count depth (naughty naughty). Here’s some code:


-- recusion test
iter=0

-- Use this function to perform your initial setup
function setup()
    print("Hello World!")
end

function recursion(n)

    local localvar=n
    --iter = iter + 1
    if localvar>5 then
        print("i have hit the bottom")
    else
        --print("iter ",iter)
        print("localvar on the way down",localvar)
        local copy=localvar
        recursion(localvar + 1)
        print("localvar coming back up",localvar)
        if copy~=localvar then print("this is a problem! this should not happen!") end
    end

end

-- This function gets called once every frame
function draw()
    -- This sets a dark background color 
    background(40, 40, 50)

    -- This sets the line thickness
    strokeWidth(5)
    print("start test")
    recursion(1)
    print("end test")
    -- Do your drawing here

end
4

Thank you that solves the problem!