begin-with-local

This package allows you to write local definitions, scoped to the surrounding begin:

(require begin-with-local)

(begin
  (local n 0)

  (define (count)
    (set! n (add1 n))
    n))

(count)   ;; => 1
(count)   ;; => 2

n         ;; error: n: unbound identifier

This is syntactic sugar around splicing-let from racket/splicing:

(require racket/splicing)

(splicing-let ([n 0])
  (define (count)
    (set! n (add1 n))
    n))

Which is in turn similar to the let-over-lambda idiom:

(define count
  (let ([n 0])
    (lambda ()
      (set! n (add1 n))
      n)))

You may also be interested in define/memo from memoize, depending on your use case.

Installation

raco pkg install begin-with-local