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Source for wiki R7RSSmallErrata version 8

author

cowan

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ipnr

127.10.177.1

name

R7RSSmallErrata

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0

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Errata from the [http://trac.sacrideo.us/wg/attachment/wiki/WikiStart/r7rs.pdf final draft of R7RS]:

1.  In Section 3.1 (Variables, syntactic keywords, and regions), the claim in paragraph 2 that all variable binding constructs can be explained in terms of `lambda` does not apply to top-level bindings.

2.  Section 7.1.5 (Transformers) doesn't make it clear that a top-level `syntax-rules` pattern must be a list pattern, not a vector pattern or an identifier pattern.

3.  In Section 6.3 (Booleans), the procedure `boolean=?` is defined to return `#t` if the arguments are all booleans and are either all `#t` or all `#f`.  The words "are all booleans and" incorrectly suggest that the value is `#f` if at least one argument is not a boolean.  In fact it is an error to apply `boolean=?` to non-booleans.

4. In Section 4.1.2 (Literal expressions), the examples `'#` and `#` should be `'#\a` and `#\a` respectively.

5. In section 7.1.1 (Lexical structure), the escape sequence `\|` is not shown as permitted in strings.  The list in Section 6.7 shows that it is equivalent to `|`.  This makes the same escape sequences valid in both strings and symbols.

6. In Section 7.3 (Derived expression types), the syntax-rules definition of `case` is incorrect; the fourth syntax rule must be moved after the fifth to avoid an improper match against the fourth rule when `=>` is present.  Here is the correct version:

{{{
 (define-syntax case
   (syntax-rules (else =>)
     ((case (key ...)
        clauses ...)
      (let ((atom-key (key ...)))
        (case atom-key clauses ...)))
     ((case key
        (else => result))
      (result key))
     ((case key
        (else result1 result2 ...))
      (begin result1 result2 ...))
     ((case key
        ((atoms ...) => result))
      (if (memv key '(atoms ...))
          (result key)))
     ((case key
        ((atoms ...) => result)
        clause clauses ...)
      (if (memv key '(atoms ...))
          (result key)
          (case key clause clauses ...)))
     ((case key
        ((atoms ...) result1 result2 ...))
      (if (memv key '(atoms ...))
          (begin result1 result2 ...)))
     ((case key
        ((atoms ...) result1 result2 ...)
        clause clauses ...)
      (if (memv key '(atoms ...))
          (begin result1 result2 ...)
          (case key clause clauses ...)))))
}}}

7. In Section 7.1.1, the lexical rule <special initial> incorrectly omits `@`.

8. Bibliographic reference ![13] should link to [http://srfi.schemers.org/srfi-4/srfi-4.html SRFI 4].

9. In section 4.2.2, add "interleaving evaluations with assignments" to the definition of `letrec*`.  Replace the meaningless example with this:

{{{
;; Returns the arithmetic, geometric, and
;; harmonic means of a nested list of numbers
(define (means ton)
  (letrec*
     ((mean
        (lambda (f g)
          (f (/ (sum g ton) n))))
      (sum
        (lambda (g ton)
          (if (null? ton)
            (+)
            (if (number? ton)
                (g ton)
                (+ (sum g (car ton))
                   (sum g (cdr ton)))))))
      (n (sum (lambda (x) 1) ton)))
    (values (mean values values)
            (mean exp log)
            (mean / /))))
}}}

Note that evaluating `(means '(3 (1 4)))` returns three values: 8/3, 2.28942848510666 (approximately), and 36/19.

10.  In section 7.1.1, add bytevectors to the alternatives for the <pattern datum> rule in 7.1.

time

2013-12-02 02:21:16

version

8