Partial R6RS library compatibility

[dpk]

Aiming for Guile/Larceny-style R6RS compatibility, rather than Chez-style R6RS total conformance. A correct R6RS library will work, but error cases will reflect Chibi’s existing style rather than what R6RS strictly demands.

Still to do:

• I’m not sure clean-up-r6rs-import handles all cases yet
• Support .sls extension for library files, looking for .chibi.sls first
• Decide what to do about SRFI 97-style library names (add redundant libraries for all of them, as in Arcfide’s chez-srfi project?)
• Decide what to do about square brackets
• Add the remaining (rnrs ...) libraries, probably piggybacking off the R6RS-cleanup SRFIs like 181 and 237/240 where appropriate
  • Decide how to support R6RS conditions within Chibi’s R7RS error object style system
• Modify the expander to use the R6RS order at least for procedure and library bodies (which is R7RS-compatible; there is a deeper issue with program bodies, see In R7RS programs, right hand sides of definitions are expanded too late larcenists/larceny#825)

If there is interest I will do these things. The only ‘core’ change is the one already made in meta-7.scm; for total support it also needs the macro expander body processing order change, which I don’t expect to be a massive change either. For square brackets it depends on the overall approach taken (#883).

[ashinn]

Thanks! In general I'm OK with a change of this size for now, but the key question is how to handle the file extensions. It was always the intention to support other languages (notably javascript), and load a different parser & evaluator based on the file extension, and that should be handled dynamically.

But if we can do so with minimal core changes I'm OK with more native R6RS support.

[dpk]

Replying to something you said in #1010 over here, because it’s more relevant to this issue.

To my knowledge, #1010 (or some equivalent change supporting the same feature) is the only change that will need to be made to init-7.scm to support an R6RS feature. It does not change anything for existing Chibi/R7RS programs.

Disclaimer: Of course, I don’t know for certain until I actually try to implement these things.

The other ‘core’ changes, as noted above, are: square bracket support in the reader (#883); supporting .sls as a file extension for libraries (even this is not strictly necessary since R6RS doesn’t say anything about file names, but .sls is the convention in the same way .sld is on R7RS); and changing the expander to expand all syntax definitions before expanding all other definitions and expressions in procedures and libraries.

Perhaps we should talk more about those changes before I make too much further progress.

[ashinn]

The other ‘core’ changes, as noted above, are: square bracket support in the reader (#883);

Support for customizing square brackets is fine. Note it's likely the default behavior will become square brackets as array literals for compatibility with Remora.

supporting .sls as a file extension for libraries (even this is not strictly necessary since R6RS doesn’t say anything about file names, but .sls is the convention in the same way .sld is on R7RS)

Probably not an issue but there's the question of what to do when both .sld and .sls are found, and the general concern about the slowdown when searching for more files.

and changing the expander to expand all syntax definitions before expanding all other definitions and expressions in procedures and libraries.

This may be a problem.