From the point of view of functional programming, a computational process to solve a problem is described as a mathematical function taking some arguments (corresponding to the data of the problem) and returning as a result its solution. Turtle Graphics can be used to describe the movements of a virtual turtle, which leaves a trail along his path on the plane. In this paper we present a functional library for Turtle Graphics that we have developed for the functional programming language Haskell. We show, by means of examples, how to use this library to graphically illustrate various concepts which are part of high school curriculum, primarily in the area of geometry. (Contains 8 figures.)