NOOB: Learning From the Book, Confused About Functions

I'm just working through the Processing textbook and I'm pretty confused about how one translates this:

vertex(90, 39);

bezierVertex(90, 39, 54, 17, 26, 83);

bezierVertex(26, 83, 90, 107, 90, 39);

into this (for automated replication);

vertex(1.0*dir, -0.7);

bezierVertex(1.0*dir, -0.7, 0.4*dir, -1.0, 0.0, 0.0);

bezierVertext(0.0, 0.0, 1.0*dir, 0.4, 1.0*dir, -0.7);

What's the formula for this?

-Pepper