NAME
bt_macros - accessing and manipulating the btparse macro table
SYNOPSIS
void bt_add_macro_value (AST * assignment,
ushort options);
void bt_add_macro_text (char * macro,
char * text,
char * filename,
int line);
void bt_delete_macro (char * macro);
void bt_delete_all_macros (void);
int bt_macro_length (char *macro);
char * bt_macro_text (char * macro,
char * filename,
int line);
DESCRIPTION
btparse maintains a single table of all macros (abbreviations)
encountered while parsing BibTeX entries. It updates this table
whenever it encounters a "macro definition" (@string) entry, and refers
to it whenever a macro is used in an entry and needs to be expanded.
(Macros are not necessarily expanded on input, although this is the
default. See bt_postprocess.) Macro definitions are only cleared when
btparse’s global cleanup function, "bt_cleanup()", is called. Thus,
unless you explicitly call "bt_delete_macro()" or
"bt_delete_all_macros()", macro definitions persist for as long as you
use the library---usually, the lifetime of your process.
FUNCTIONS
You can use the following functions to add macros, delete them, and
query their values---thus interfering with btparse’s normal operation
on the fly.
bt_add_macro_text ()
void bt_add_macro_text (char * macro,
char * text,
char * filename,
int line);
Defines a new macro, or redefines an old one. "macro" is the name
of the macro, and "text" is the text it should expand to.
"filename" and "line" are just used to generate any warnings about
the macro definition; if they don’t apply, specify "NULL" for
"filename" and
for "line". The only such warning occurs when you redefine an old
macro: its value is overridden, and "bt_add_macro_text()" issues a
warning saying so.
For instance, when parsing this macro definition entry:
@string{fubar = "Fouled Up Beyond All Recognition"}
the library (in particular, the post-processing code called after
an entry is successfully parsed) will ultimately do this:
bt_add_macro_text ("fubar", "Fouled Up Beyond All Recognition",
filename, line);
This in turn will cause the macro "fubar" to be expanded
appropriately whenever the post-processing code sees it in any
future entries.
bt_add_macro_value ()
void bt_add_macro_value (AST * assignment,
ushort options);
This function is mainly for internal use by the library, but it’s
available to you if you ever find yourself with a little bit of AST
representing a macro definition, and you want to set the macro
yourself (rather than letting the library’s post-processing code
take care of it for you). "assignment" must be an AST node as
returned by "bt_next_field()". Unlike most other btparse functions
that take an "options" argument, "options" here tells how the value
in "assignment" was post-processed. This is needed because macro
values have to be processed in a special way to be valid in future
expansions; if this one wasn’t processed like that,
"bt_add_macro_value()" will do it for you. If you don’t know how
the value was post-processed, just supply for "options"---that’s
guaranteed to describe something different from "the right way" for
macros, so the post-processing will be done correctly.
The processing done to macro values is mainly to ensure that we can
get away with storing just a string in the macro table: macros
invoked by the macro are themselves expanded, and all sub-strings
are concatenated. For instance, if btparse parses these entries:
@string{and = " and "}
@string{jim_n_bob = "James Smith" # and # "Bob Jones"}
then the value stored for "jim_n_bob" should obviously be the
string "James Smith and Bob Jones". To ensure this, btparse has to
process the value of "and" differently from most BibTeX strings: in
particular, whitespace is not collapsed before the string is
stored. That way, the correct value, " and ", is interpolated into
the value of "jim_n_bob". Thus, all macro values have sub-macros
expanded and strings concatenated before they are stored, but
whitespace is not collapsed until the macro is used in a regular
entry.
This function calls "bt_add_macro_text()", so the same proviso
about redefining old macros applies---a warning will be issued, and
the old value lost.
bt_delete_macro ()
void bt_delete_macro (char * macro);
Deletes a macro from the macro table. If "macro" isn’t defined,
takes no action.
bt_delete_all_macros ()
void bt_delete_all_macros (void);
Deletes all macros from the macro table.
bt_macro_length ()
int bt_macro_length (char *macro);
Returns the length of a macro’s expansion text. If the macro is
undefined, returns 0; no warning is issued.
bt_macro_text ()
char * bt_macro_text (char * macro,
char * filename,
int line);
Returns the expansion text of a macro. If the macro is not
defined, issues a warning and returns "NULL". "filename" and
"line" are used for generating this warning; if they don’t apply
(i.e. you’re not expanding the macro as a result of finding it in
some file), supply "NULL" for "filename" and for "line".
SEE ALSO
btparse
AUTHOR
Greg Ward <gward@python.net>