(Or "contraction") The process of transforming an expression
according to certain reduction rules. The most important
forms are beta reduction (application of a lambda
abstraction to one or more argument expressions) and delta
reduction (application of a mathematical function to the
required number of arguments).
An evaluation strategy (or reduction strategy), determines
which part of an expression (which redex) to reduce first.
There are many such strategies.
See graph reduction, string reduction, normal order
reduction, applicative order reduction, parallel
reduction, alpha conversion, beta conversion, delta
conversion, eta conversion.
