I've just published draft #8 of SRFI 189. It was submitted by John Cowan, co-author of the SRFI.

Here are John's comments on the draft:

If we are already in LC, we should do a second LC.

John and Wolfgang have made substantial additions to the text and the sample implementation, so they're requesting a second "last call" period. If you'd like to comment, please submit your feedback before 2020-07-08.

Here is the commit summary:

• Implement multiple-argument versions of maybe=? and either=?.
• Update maybe / either-ref to Draft 7.
• Rename "generator" and "truth" conversions.
• values->either: Allow multiple default objects.
• Rename "two-values" conversions.
• Update maybe / either-compose to Draft 7.
• Add single-seed fast path to -unfold procedures.
• Tune single-value paths of maybe / either-ref.
• Further tuning of -ref procedures.
• Simplify maybe= and either=.
• Add tests for maybe= / either= with more than two arguments.
• Tune single-value path of -filter and -remove procedures.
• call successor during -unfold
• Revert "call successor during -unfold"
• Minor comment cleanup and page reformat.
• Simplify single-value fast paths with macros.
• Tests: rename macro.
• Remove artifact named let.
• Fix bug in maybe- / either-unfold and add test.
• unfold now an anamorphism, multitruth renamed to list-truth, Either protocol converters
• Add either->truth.
• Fix procedure name in error message.
• Rename "generation" protocol conversions.
• Add list->maybe and list->either.
• Add "list-truth" protocol conversions.
• Update maybe / either-unfold to Draft 8 versions.
• Fix missing paren.
• Update tests for Draft 8.
• Use assume to signal errors where the SRFI says "it is an error".
• Remove non-portable tests for error conditions.
• editorial
• Add truth->either. Update tests.
• slight cleanups
• editorial
• moved conversion to constructors
• Move conversions to constructor section.
• Copy list arguments to raw-just, etc., where necessary.
• Additional tuning of single-value payload paths.
• Minor typo and grammatical fixes.
• Fix typo.
• minor correction
• New syntactic forms: Initial import.
• and, or, let*
• Ensure base values of -and-let* forms are unwrapped.
• Add type checks to and/or macros.
• Fix typo.
• editorial
• Fix -and-let* bugs which caused correct expression to raise errors.
• clarify maybe-let*
• Revert "Fix -and-let* bugs which caused correct expression to raise errors."
• let* forms: Enforce Maybe/Either-valued claws in body-less cases.
• Rename macros: and-let* -> let*.
• Fix names in macro body.
• Add tests for and, or, and let* forms.
• Replace unused pattern variable with underscore.
• Add generation->either and either->generation.
• Tests for Either generation conversions.
• Tuning: eliminate maybe-ref in several procedures.
• Tuning: eliminate some uses of -bind and -ref procedures.
• Eliminate -bind and -ref from map and fold procedures.
• Minor style changes. Comment improvement.
• Minor tuning of either-swap.
• Use helper type-check macro in conditional forms.
• Refactor maybe/either-let* to efficiently catch ill-typed bodies.
• Switch to new standard SRFI header format.
• Update abstract.
• Remove trailing whitespace.
• Publish eighth draft.

Here's the diff:

https://github.com/scheme-requests-for-implementation/srfi-189/compare/draft-7..draft-8

Regards,


SRFI Editor