Editing Combinatory logic (section)

=== Reduction in combinatory logic ===

In combinatory logic, each primitive combinator comes with a reduction rule of the form

:{{math|1=(''P'' ''x''<sub>1</sub> ... ''x<sub>n</sub>'') = ''E''}}

where ''E'' is a term mentioning only variables from the set {{math|{{mset|''x''<sub>1</sub> ... ''x<sub>n</sub>''}}}}. It is in this way that primitive combinators behave as functions.