mat.newrdn() "positive" logic works, but only by accident

[dcuny]

In Matrix.lua, the function mat.newrdn() intends to set the parameter positive to false if it's not passed (i.e it's a nil value).

  --New random matrix
  function mat.newrdn(rows,cols,positive)
  positive = false or positive
  local grid ={}
  grid.rows = rows
  grid.cols = cols
  grid.matrix = {}
  local j = 1
  for i=1,rows do
    grid.matrix[i] = {}
    for k=1,cols do
      if positive then
        grid.matrix[i][k] = math.random()
      else
        grid.matrix[i][k] = math.random(-1,0) + math.random()
      end
      j = j+1
    end
  end
    return grid
end

As written, the line:

  positive = false or positive

will always behave as:

  positive = positive

because false will always evaluate to false, and cause or to return the right hand value, positive.

The code should have been written as:

  positive = positive or false

That is, if positive wasn't passed as a parameter and so is set to nil, the line should set it to false.

The code accidentally works because if* treats nil the same as false, so even though the line doesn't change the value of positive, it still ends up taking the correct branch of the user hasn't specified a value for positive.

Still, the line should be corrected to match the intent.