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Walrus.md

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What we need to implement an R7RS runtime over R6RS

Lexical syntax

  • Support #u8 rather than #vu8
  • Support datum labels (#n= and #n#)
  • Support #true and #false
  • Vertical-bar escapes around symbols

Syntax (and associated procedures)

  • Support include syntax with the (include) library
  • Support cond-expand syntax (somehow)
  • Support delay-force syntax and promise? and make-promise procedure (may need to reimplement promises)
  • Support SRFI 39 parameters (Chez's parameters aren't compatible)
  • Add support for (... <template>), which removes the special meaning of ellipsis
  • syntax-error needs to supply a who argument
  • Support define-values syntax
  • Translate R7RS define-record-type to R6RS define-record-type; the hard part is the constructor.

Libraries

  • Reshape define-library forms into library forms with the help of the include library

Equivalence predicates

  • Location tags for procedures (used by eq?)

Numbers

  • finite? is true of non-real numbers if both the real and the imaginary parts are finite

  • infinite? is true of non-real numbers if either the real or the imaginary parts or both are non-finite

  • nan? is true of non-real numbers if either the real or the imaginary parts or both are NaN

  • Define floor/, floor-quotient, floor-remainder, truncate/, truncate-quotient, truncate-remainderin terms ofdivandmod`: see r6rs-lib Chapter 19

  • Define rationalize per IEEE 1178

Pairs and lists

  • Define make-list
  • Define list-ref
  • Define list-set!
  • Define member in terms of member and memp
  • Define assoc in terms of assoc and assp
  • Define list-copy

Characters

  • Define digit-value
  • Accept \| string escape

Strings

  • Define string-copy!
  • Define string-fill!

Vectors

  • Define vector->string and string->vector
  • Define vector-copy and vector-copy!

Bytevectors

  • bytevector-copy takes start and end optional arguments
  • bytevector-copy! takes different arguments
  • Define bytevector-append
  • utf8->string and string->utf8 take start and end optional arguments

Exceptions

  • error needs to supply a who argument
  • error-object-message and error-object-irritants are condition-message and condition-irritants (with safety checks)

Environments and evaluation

  • eval accepts definitions
  • Define scheme-environment and null-environment based on (rnrs r5rs)

Input and output

  • Define open-binary-input-file and open-binary-output-file using open-file-input-port and open-file-output-port
  • Define input-port-open? and output-port-open? (using exceptions somehow)
  • Define get-output-string using second value of open-string-output-port
  • Define get-output-bytevector using second value of open-bytevector-output-port
  • Define read-bytevector and write-bytevector
  • Define read-bytevector! and write-bytevector!
  • Define peek-char and peek-u8 using lookahead-char and lookahead-u8'
  • Define read based on R7RS lexical syntax
  • Define write-simple as write
  • Define write-circular and write-shared
  • Define load
  • Define command-line, exit, get-environment-variable, get-environment-variables, current-second, current-jiffy, jiffies-per-second, features (not portable)