Chapter 6. Plotting Mathematical Expressions

In this chapter, we will create an application which will plot arbitrary mathematical expressions on a Windows Presentation Foundation (WPF)-based graphical surface. We will be using the GoF observer pattern for wiring expression input control and the rendering surface. In the process, we will develop a library which can evaluate arbitrary arithmetic expressions on the fly. The expression evaluator will support basic arithmetic operators (+, -, *, /, unary +/- ), trigonometric functions, and a pseudo variable ($t) which can represent the value of X-axis in a 2D Plane. During the course of this chapter, as a reader, you will learn the following:

• The observer pattern
• Parsing mathematical expressions using recursive descent
• Modeling abstract syntax tree (AST) as a composite
• The interpreter pattern
• The builder pattern
• Elementary WPF 2D graphics