The <span>letrec</span> namebinding construct

Lecture 1 - Page 41 : 49

Programming Paradigms
Introduction to Functional Programming in Scheme

The letrec namebinding construct

The letrec name binding construct allows for definition of mutually recursive functions


 
(letrec ((n<sub>1</sub> e<sub>1</sub>)
         ...
         (n<sub>k</sub> e<sub>k</sub>))
    body-expr)

(letrec ((f1 (lambda (...) ... (f2 ...)))
         (f2 (lambda (...) ... (f1 ...)))
        )
  body-expr)

An schematic example of a typical application of letrec for local definition of two mutually recursive functions.

Characteristics of letrec
- Each of the name bindings have effect in the entire letrec construct, including e₁ ... e_k
- letrec can be implemented by assignments to the bound names