Problem updating a variable in a loop

Questions & Help Questions
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1

How i acn upadate the value of the variable “square=0” as mention in my code so that after every loop it will update it by addind + 1 in “square=0”

this is my code :

def findcontours(path) do
    #squares=0
    {:ok, imgGrey} = OpenCV.imread(path, flags: OpenCV.cv_IMREAD_GRAYSCALE())
    {:ok, {_, thrash}} = OpenCV.threshold(imgGrey, 240, 255, OpenCV.cv_THRESH_BINARY())
    {:ok, {contours, _}} =OpenCV.findContours(thrash, OpenCV.cv_RETR_TREE(), OpenCV.cv_CHAIN_APPROX_NONE())

    square = 0
    for contour <- contours do
      {:ok,peri} = OpenCV.arcLength(contour,true)
      {:ok,approx} = OpenCV.approxPolyDP(contour, 0.01 * peri,true)
      ap=OpenCV.Nx.to_nx(approx)
      {len,_,_}=Nx.shape(ap)


      if len==4 do #to bound squares from the countor
        {:ok,{x1, y1, w, h}}= OpenCV.boundingRect(approx)
        aspectRatio = (w/1)/h
        if aspectRatio >= 0.95 and aspectRatio <= 1.05 and (y1+h)*(x1+w) < 985000 do
          square=square +1
        end
      end
    end
  end

pls help me to update my value of square as i know there i a big problem of scope in elixir and also it is immutable so pls help me for this.

or suggest me another way so that i can do the whole process by another way if possible.