There can be great variation in shape of leaves. Neverthless they are fairly simple shapes. How far are we in describing the shape of leaves in a mathematically rigorous way? Do we have a general formula that can be used to describe all shapes of leaves (or, at least, a reasonably large subset)?
There are algorithms which can be used to describe leaves, if that is what you mean.
The following description takes into account that leaf shape is not solely a function of genetics, but is also effected by environment. It also models how different growth rates within the cells have consequences. Mutant, cloning cells are also factored into the description.
The mathematical model has interesting allometric implications.
Here is a very readable paper (PDF),which endeavours to describe differences using mathematics and for which for which we can thank Cornell University Library for hosting the paper and Lawrence Livermore National Laboratory.