shorthand for ((lambda () ))

Question

Is there a shorthand in scheme for ((lambda () ))

For example, instead of

((lambda ()
    (define x 1)
    (display x)))

I would love to be able to do something like

(empty-lambda
    (define x 1)
    (display x))

score 10 · Accepted Answer · answered Oct 18 '11 at 03:22

10

The usual idiom for that is

(let ()
  (define x 1)
  (display x))

which you can of course turn into a quick macro:

(define-syntax-rule (block E ...) (let () E ...))

answered Oct 18 '11 at 03:22

Eli Barzilay

2

I thought the obvious answer would be to use `begin`, like: `(begin (define x 1) (display x))` Turns out to be obvious and wrong, see http://stackoverflow.com/questions/1683796/how-can-you-rewrite-begin-in-scheme/1683842#1683842. – Shannon Severance Oct 18 '11 at 21:11

score 3 · Answer 2 · answered Oct 18 '11 at 07:10

3

Why not just

(let
    ((x 1))
    (display x))

answered Oct 18 '11 at 07:10

newacct

score 3 · Answer 3 · answered Oct 18 '11 at 15:32

3

Racket provides the block form, which works like this:

#lang racket
(require racket/block)
(block
 (define x 1)
 (display x))

answered Oct 18 '11 at 15:32

score 2 · Answer 4 · edited Nov 14 '11 at 02:47

2

(define-syntax empty-lambda
  (syntax-rules ()
    ((empty-lambda body ...)
      ((lambda () body ...)))))

edited Nov 14 '11 at 02:47

Bill the Lizard

answered Oct 18 '11 at 03:21

user448810

Yes I realize that but I wanted something built-in. Thanks though! – Cam Oct 18 '11 at 03:25

4 Answers4