I've just published draft #3 of SRFI 155.  It was submitted
by Marc Nieper-Wißkirchen, author of the SRFI.

  <https://srfi.schemers.org/srfi-155/>

Here are Marc's comments on the draft:

  The new draft incorporates a major improvement to the
  semantics of the pair delay and force, making delay-force
  unnecessary.  It is shown through an efficient sample
  implementation that a Scheme system can ensure that
  iterative lazy algorithms run in bounded space without
  needing the aid of the user (by writing delay-force).

  Other changes:

  - Use the new terminology of SRFI 154, which replaces dynamic environment by dynamic extent.
  - Update included sample implementation of SRFI 154.
  - Update sample R7RS implementation to the new semantics, requiring SRFI 157 for complete correctness.
  - Provide a Racket module.
  - Clarify semantics of (forcing-extent).

  Commit Summary

  - Update SRFI 154 implementation
  - Change proposed library from (scheme lazy) to (scheme promise)
  - Minor grammar fix
  - Major feature update

  File Changes

  M Makefile (7)
  M srfi-155.html (324)
  A srfi/154.chibi.scm (38)
  A srfi/154.closed-lambda.scm (29)
  A srfi/154.rkt (61)
  M srfi/154.scm (26)
  M srfi/154.sld (21)
  A srfi/155.rkt (36)
  A srfi/155/implementation.157.scm (111)
  R srfi/155/implementation.lazy.scm (35)
  M srfi/155/implementation.sld (15)
  M srfi/155/reflection.sld (2)
  A srfi/155/test.rkt (31)
  A srfi/155/test.scm (82)
  M srfi/155/test.sld (56)
  A tests.rkt (28)

Here's the diff:

  <https://github.com/scheme-requests-for-implementation/srfi-155/compare/ee62ed19ba7123173088634a773e6cafab31c11d...4bab073539dfbdcc947f3be09971299dd25c2657>

Regards,

SRFI Editor