You have a rectangular piece of paper of width and length . You pick up the left side and fold it to the right side, like so:
Which function describes the new position of a point on the paper after the fold?
f(x, y, W, L) = \left\{ \begin{array}{rl} (W-x,y) &\mbox{ if \$x<\frac{W}{2}\$} \\ (x, y) &\mbox{ otherwise} \end{array} \right.
f(x, y, W, L) = \left\{ \begin{array}{rl} (W^{2}-x,y+L-W) &\mbox{ if \$x>\frac{W}{2}\$} \\ (x, y) &\mbox{ otherwise} \end{array} \right.
Details and assumptions: