Stak Scheme updates

@raviqqe

March 17, 2024

Contents

• Progress
  • Library system fixes
• Future work

Library system update

import

• (rename ...)
  • Renames each imported symbol.
• (prefix ...)
  • Puts a prefix to imported symbols.

export

• (rename ...)
  • Renames an exported symbol.

Library system bug fixes

• Macro expansion
• Quotes

Macro expansion

• Literals in macros need to be matched on expansion.
• Previously, they were not properly matched across library boundaries.

(define-syntax cond
  (syntax-rules (else =>)
    ((_ (else result1 result2 ...))
      (begin result1 result2 ...))

• The literals need to be exported too.

(export
  ; ...

  else
  =>)

Quotes

• ', `, ,, and ,@
• (quote ...) is actual syntax.
• Quoted symbols can be compared by eq? for equality.

'(1 2 3)
`(1 ,x 3)

'(x y z) ; <- ?

Quotes

• Are quoted symbols need to be different across libraries?
  • The answer seems to be no according to the other implementations.

(define-library (foo bar)
  (import (scheme base))

  (begin
    (define x '(x y z))

    ; This is `(define x (quote (x y z)))`.
    ; But is it `(define foo/bar/x (quote (foo/bar/x foo/bar/y foo/bar/z)))`?
    ))

Others

• Removal of hacks
  • Parsing "keywords"
    • syntax-rules, define-syntax, ..., etc. are normal macros now.
  • Built-in symbols now have string representations.
• Compiler optimization
  • Integration test: 3 hours -> 1.5 hours

Future work

• Compiler performance improvements
• eval procedure

Summary

• Fixing a library system is fun!