An affine transformation is a linear transformation followed by a translation; i.e. it is a function
\x -> A*x + b
Where A is a linear transformation. Affine transformations are the set of image transformations supported by Graphics.DrawingCombinators, roughly translate, rotate, scale, and compositions thereof.
An Affine transformation from R2 to R2.
[[Affine]] = R2 -> R2
With the Monoid instance
[[inverse x]] = inverse [[x]]
If the transformation is not invertible, this operation is undefined.
Multiply this Affine by the top of the OpenGL matrix stack. Don't mind this, it's an implementation detail.