NAME

       bt_misc - miscellaneous BibTeX-like string-processing utilities

SYNOPSIS

          void bt_purify_string (char * string, btshort options);
          void bt_change_case (char transform, char * string, btshort options);

DESCRIPTION

       bt_purify_string()
              void bt_purify_string (char * string, btshort options);

           "Purifies" a "string" in the BibTeX way (usually used for generating sort keys).
           "string" is modified in-place.  "options" is currently unused; just set it to zero for
           future compatibility.  Purification consists of copying alphanumeric characters,
           converting hyphens and ties to space, copying spaces, and skipping (almost) everything
           else.

           "Almost" because "special characters" (used for accented and non-English letters) are
           handled specially.  Recall that a BibTeX special character is any brace-group that
           starts at brace-depth zero whose first character is a backslash.  For instance, the
           string

              {\foo bar}Herr M\"uller went from {P{\r r}erov} to {\AA}rhus

           contains two special characters: "{\foo bar}" and "\AA".  Neither the "\"u" nor the
           "\r r" are special characters, because they are not at the right brace depth.

           Special characters are handled as follows: if the control sequence (the TeX command
           that follows the backslash) is recognized as one of LaTeX's "foreign letters" ("\oe",
           "\ae", "\o", "\l", "\ae", "\ss", plus uppercase versions), then it is converted to a
           reasonable English approximation by stripping the backslash and converting the second
           character (if any) to lowercase; thus, "{\AA}" in the above example would become
           simply "Aa".  All other control sequences in a special character are stripped, as are
           all non-alphabetic characters.

           For example the above string, after "purification," becomes

              barHerr Muller went from Pr rerov to Aarhus

           Obviously, something has gone wrong with the word "P{\r r}erov" (a town in the Czech
           Republic).  The accented `r' should be a special character, starting at brace-depth
           zero.  If the original string were instead

              {\foo bar}Herr M\"uller went from P{\r r}erov to {\AA}rhus

           then the purified result would be more sensible:

              barHerr Muller went from Prerov to Aarhus

           Note the use of a "nonsense" special character "{\foo bar}": this trick is often used
           to put certain text in a string solely for generating sort keys; the text is then
           ignored when the document is processed by TeX (as long as "\foo" is defined as a no-op
           TeX macro).  This assumes, of course, that the output is eventually processed by TeX;
           if not, then this trick will backfire on you.

           Also, bt_purify_string() is adequate for generating sort keys when you want to sort
           according to English-language conventions.  To follow the conventions of other
           languages, though, a more sophisticated approach will be needed; hopefully, future
           versions of btparse will address this deficiency.

       bt_change_case()
              void bt_change_case (char transform, char * string, btshort options);

           Converts a string to lowercase, uppercase, or "non-book title capitalization", with
           special attention paid to BibTeX special characters and other brace-groups.  The form
           of conversion is selected by the single character "transform": 'u' to convert to
           uppercase, 'l' for lowercase, and 't' for "title capitalization".  "string" is
           modified in-place, and "options" is currently unused; set it to zero for future
           compatibility.

           Lowercase and uppercase conversion are obvious, with the proviso that text in braces
           is treated differently (explained below).  Title capitalization simply means that
           everything is converted to lowercase, except the first letter of the first word, and
           words immediately following a colon or sentence-ending punctuation.  For instance,

              Flying Squirrels: Their Peculiar Habits. Part One

           would be converted to

              Flying squirrels: Their peculiar habits. Part one

           Text within braces is handled as follows.  First, in a "special character" (see above
           for definition), control sequences that constitute one of LaTeX's non-English letters
           are converted appropriately---e.g., when converting to lowercase, "\AE" becomes
           "\ae").  Any other control sequence in a special character (including accents) is
           preserved, and all text in a special character, regardless of depth and punctuation,
           is converted to lowercase or uppercase.  (For "title capitalization," all text in a
           special character is converted to lowercase.)

           Brace groups that are not special characters are left completely untouched: neither
           text nor control sequences within non-special character braces are touched.

           For example, the string

              A Guide to \LaTeXe: Document Preparation ...

           would, when "transform" is 't' (title capitalization), be converted to

              A guide to \latexe: Document preparation ...

           which is probably not the desired result.  A better attempt is

              A Guide to {\LaTeXe}: Document Preparation ...

           which becomes

              A guide to {\LaTeXe}: Document preparation ...

           However, if you go back and re-read the description of bt_purify_string(), you'll
           discover that "{\LaTeXe}" here is a special character, but not a non-English letter:
           thus, the control sequence is stripped.  Thus, a sort key generated from this title
           would be

              A Guide to  Document Preparation

           ...oops!  The right solution (and this applies to any title with a TeX command that
           becomes actual text) is to bury the control sequence at brace-depth two:

              A Guide to {{\LaTeXe}}: Document Preparation ...

SEE ALSO

       btparse

AUTHOR

       Greg Ward <gward@python.net>