UFL Specification and User Manual 0.3 - FEniCS Project

Chapter 4Internal Representation DetailsThis chapter explains how UFL forms and expressions are represented indetail. Most operations are mirrored by a representation class, e.g., Sum andProduct, all which are subclasses of Expr. You can import all of them fromthe submodule ufl.classes byfrom ufl.classes import *TODO: Automate the construction of class hierarchy figures using ptex2tex.4.1 Structure of a FormTODO: Add class relations figure with Form, Integral, Expr, Terminal, Operator.EachFormownsmultipleIntegralinstances,eachassociatedwithadifferentMeasure. An Integral owns a Measure and an Expr, which represents theintegrand expression. The Expr is the base class of all expressions. It hastwo direct subclasses Terminal and Operator.75