What are "reduction semantics"? Please explain the use of PLT Redex in layman's term

Question

Somebody please explain the usage of reduction semantics and the PLT Redex in simpler language.

Thanks.

Answer 1

Reduction semantics is a computation technique that involves replacing an expression by an equivalent (and hopefully smaller) expression until no more replacement is possible. If a language is Turing-complete, there are expressions that never stop replacing.

Reduction is usually notated by a right arrow, and it's best explained by example:

(3 + 7) + 5   -->  10 + 5  -->  15

This shows the standard reduction semantics for arithmetic expressions. The expression 15 cannot be reduced any further.

Hope this helps.