A normal let
form binds each value to its corresponding identifier, before executing the body. With a "named let
", the body can then recursively be re-executed, passing a new value for each identifier.
#lang racket
(let sum-of-list ([l '(1 2 3)])
(if (null? l)
0
(+ (car l) (sum-of-list (cdr l)))))
;; => 15
It is common to use rec
as the name for the let, which gives:
#lang racket
(let rec ([l '(1 2 3 4 5)])
(if (null? l)
0
(+ (car l) (rec (cdr l)))))
;; => 15