2.8.2.6 Extra–SRFI recommendations

This SRFI recommends the following:

• A SRFI be defined for shared–text substrings, allowing programs to be written that actually rely on the shared–storage properties of these data structures.
• A SRFI be defined for manipulating Unicode text: various normalisation operations, collation, searching, etc. Collation operations might be parameterised by a “collation” structure representing collation rules for a particular locale or language.

  Alternatively, a data structure specifying collation rules could be activated with dynamic scope by special procedures, possibly overridden by allowing collation rules to be optional arguments to procedures that need to order strings, e.g.

  (with-locale* denmark-locale
    (lambda ()
      (f x)
      (g 42)))
  
  (with-locale taiwan-locale
    (f x)
    (h denmark-locale)
    (g 42))
  
  (set-locale! denmark-locale)
  

• A SRFI be defined for manipulating characters that is portable across at least ASCII, Latin–1 and Unicode.
  • - For backwards–compatibility, char-upcase and char-downcase should be defined to use the one–to–one locale–insensitive and context–insensitive case mappings given by Unicode’s UnicodeData.txt table.
  • - Numeric codes for standard functions that map between characters and integers should be required to use the Unicode/Latin–1/ASCII mapping. This allows programmers to write portable code.
  • - char-titlecase be added to char-upcase and char-downcase.
  • - char-titlecase? be added to char-upcase? and char-downcase?.
  • - Title/up/down–case functions be added to the character–processing suite which allow 1->n case maps by returning immutable, possibly–multi–character strings instead of single characters. These case mappings need not be locale–sensitive or context–sensitive.

These recommendations are not a part of the SRFI-13 spec. Note also that requiring a Unicode/Latin-1/ASCII interface to integer/char mapping functions does not imply anything about the actual underlying encodings of characters.