Import a r6rs library from another r6rs library in the same directory?

Questions & Answers
1

I can easily require a r6rs library file in the same directory from a Racket program:

a1.rkt:

#lang racket

(require "b2.rkt")

(foo)

a2.rkt:

#!r6rs

(library (a2)
  (export foo)
  (import (rnrs))

  (define (foo)
    "hello, this is foo"))

$ racket a1.rkt 
"hello, this is foo"

Now I want to import a second r6rs library from my first one:

b1.rkt:

#lang racket

(require "b2.rkt")

(foo)

b2.rkt:

#!r6rs

(library (b2)
  (export foo)
  (import (rnrs) ???)

  (define (foo)
    (bar)))

b3.rkt:

#!r6rs

(library (b3)
  (export bar)
  (import (rnrs))

  (define (bar)
    "hello, this is bar"))

Looking at 5 Libraries and Collections it appears that all valid r6rs library names reference a directory path, so maybe the best I can do is put b3.rkt in a subdirectory?

b2.rkt:

#!r6rs

(library (b2)
  (export foo)
  (import (rnrs) (b b3))

  (define (foo)
    (bar)))

Moving b3.rkt into a subdirectory b, I can use:

racket -S . b1.rkt

and that works.