Editing Reduce (computer algebra system) (section)

== Programming paradigms ==
REDUCE's user-level language supports several [[Programming paradigm|programming paradigms]], as illustrated in the [[#Algebraic programming examples|algebraic programming examples]] below.

Since it is based on Lisp, which is a [[functional programming]] language, REDUCE supports functional programming and all statements have values (although they are not always useful). REDUCE also supports [[procedural programming]] by ignoring statement values. Algebraic computation usually proceeds by transforming a mathematical expression into an equivalent but different form. This is called ''simplification'', even though the result might be much longer. (The name ''REDUCE'' is a [[pun]] on this problem of ''intermediate expression swell''!) In REDUCE, simplification occurs automatically when an expression is entered or computed, controlled by ''simplification rules'' and ''switches''. In this way, REDUCE supports [[Rule-based system|rule-based programming]], which is the classic REDUCE programming paradigm. In early versions of REDUCE, rules and switches could only be set globally, but modern REDUCE also supports local setting of rules and switches, meaning that they control the simplification of only one expression. REDUCE programs often contain a mix of programming paradigms.