[racket users] module question

[Kevin Forchione]

Is there a way to define 2 modules within a file and reference them or is a file limited to 1 module only (but may have multiple submodules)?

Here’s a small sample:

#lang racket

(module A racket
˘ (provide X)
(define X 'foo))

(module B racket
(require 'A)
(printf "X=~a~%" X))

Apparently, as I understand it, I’m already nesting modules within the #lang racket. But I’m not sure how to require A from within B in this situation.

Kevin

[Sorawee Porncharoenwase]

You need:

(module B racket
  (require (submod ".." A))
  (printf "X=~a~%" X))

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[Luis Sanjuán]

As Sorawee has said. To expand a bit.

First,

#lang modname

is a shorthand for:

(module a-name modname)

where a-name derives from the filename.

So, modules within are actually submodules.

On the other hand, the .. in the submod is a relative module path. The symbol is borrowed, I believe, from Unix.

where '.' means the current path, and '..' means the parent of the current path. Here,

'..' points to the enclosing module.

[Kevin Forchione]

On Aug 6, 2019, at 4:06 PM, Sorawee Porncharoenwase <sorawe...@gmail.com> wrote:

(module B racket
  (require (submod ".." A))
  (printf "X=~a~%" X))

Why doesn’t printf display anything ? 

Kevin 

[Kevin Forchione]

Oh, wait. modules are “lazy” until they’re required. Something like that. I think I’m beginning to understand. :) 

#lang racket

(module A racket

  (provide X)

  (define X 5)

  (printf "A.X=~a~%" X))

(module B racket

  (require (submod ".." A))

  (printf "B.X=~a~%" X))

(require ‘B)

Kevin