Lecture overview -- Keyboard shortcut: 'u'  Previous page: Normal forms -- Keyboard shortcut: 'p'  Next page: An example of normal versus applicative evaluation -- Keyboard shortcut: 'n'  Lecture notes - all slides and notes together  slide -- Keyboard shortcut: 't'  Textbook -- Keyboard shortcut: 'v'  Help page about these notes  Alphabetic index  Course home    Lecture 5 - Page 14 : 26
Functional Programming in Scheme
The Order of Evaluation
The ordering of reductions

Given a complex expression, there are many different orderings of the applicable reductions

Using normal-order reduction, the first reduction to perform is the one at the outer level of the expression

Using applicative-order reduction, the first reduction to perform is the inner leftmost reduction

  • Normal-order reduction represents evaluation by need

  • Applicative-order reduction evaluates all constituent expressions, some of which are unnecessary or perhaps even harmful. As such, there is often a need to control the evaluation process withspecial formsthat use a non-standard evaluation strategy