1BT_MACROS(1)                        btparse                       BT_MACROS(1)
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NAME

6       bt_macros - accessing and manipulating the btparse macro table
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SYNOPSIS

9          void bt_add_macro_value (AST *  assignment,
10                                   btshort options);
11          void bt_add_macro_text (char * macro,
12                                  char * text,
13                                  char * filename,
14                                  int    line);
15
16          void bt_delete_macro (char * macro);
17          void bt_delete_all_macros (void);
18
19          int bt_macro_length (char *macro);
20          char * bt_macro_text (char * macro,
21                                char * filename,
22                                int line);
23

DESCRIPTION

25       btparse maintains a single table of all macros (abbreviations)
26       encountered while parsing BibTeX entries.  It updates this table
27       whenever it encounters a "macro definition" (@string) entry, and refers
28       to it whenever a macro is used in an entry and needs to be expanded.
29       (Macros are not necessarily expanded on input, although this is the
30       default.  See bt_postprocess.)  Macro definitions are only cleared when
31       btparse's global cleanup function, "bt_cleanup()", is called.  Thus,
32       unless you explicitly call "bt_delete_macro()" or
33       "bt_delete_all_macros()", macro definitions persist for as long as you
34       use the library---usually, the lifetime of your process.
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FUNCTIONS

37       You can use the following functions to add macros, delete them, and
38       query their values---thus interfering with btparse's normal operation
39       on the fly.
40
41       bt_add_macro_text ()
42              void bt_add_macro_text (char * macro,
43                                      char * text,
44                                      char * filename,
45                                      int    line);
46
47           Defines a new macro, or redefines an old one.  "macro" is the name
48           of the macro, and "text" is the text it should expand to.
49           "filename" and "line" are just used to generate any warnings about
50           the macro definition; if they don't apply, specify "NULL" for
51           "filename" and 0 for "line".  The only such warning occurs when you
52           redefine an old macro: its value is overridden, and
53           "bt_add_macro_text()" issues a warning saying so.
54
55           For instance, when parsing this macro definition entry:
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57              @string{fubar = "Fouled Up Beyond All Recognition"}
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59           the library (in particular, the post-processing code called after
60           an entry is successfully parsed) will ultimately do this:
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62              bt_add_macro_text ("fubar", "Fouled Up Beyond All Recognition",
63                                 filename, line);
64
65           This in turn will cause the macro "fubar" to be expanded
66           appropriately whenever the post-processing code sees it in any
67           future entries.
68
69       bt_add_macro_value ()
70              void bt_add_macro_value (AST *  assignment,
71                                       btshort options);
72
73           This function is mainly for internal use by the library, but it's
74           available to you if you ever find yourself with a little bit of AST
75           representing a macro definition, and you want to set the macro
76           yourself (rather than letting the library's post-processing code
77           take care of it for you).  "assignment" must be an AST node as
78           returned by "bt_next_field()".  Unlike most other btparse functions
79           that take an "options" argument, "options" here tells how the value
80           in "assignment" was post-processed.  This is needed because macro
81           values have to be processed in a special way to be valid in future
82           expansions; if this one wasn't processed like that,
83           "bt_add_macro_value()" will do it for you.  If you don't know how
84           the value was post-processed, just supply 0 for "options"---that's
85           guaranteed to describe something different from "the right way" for
86           macros, so the post-processing will be done correctly.
87
88           The processing done to macro values is mainly to ensure that we can
89           get away with storing just a string in the macro table: macros
90           invoked by the macro are themselves expanded, and all sub-strings
91           are concatenated.  For instance, if btparse parses these entries:
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93              @string{and = " and "}
94              @string{jim_n_bob = "James Smith" # and # "Bob Jones"}
95
96           then the value stored for "jim_n_bob" should obviously be the
97           string "James Smith and Bob Jones".  To ensure this, btparse has to
98           process the value of "and" differently from most BibTeX strings: in
99           particular, whitespace is not collapsed before the string is
100           stored.  That way, the correct value, " and ", is interpolated into
101           the value of "jim_n_bob".  Thus, all macro values have sub-macros
102           expanded and strings concatenated before they are stored, but
103           whitespace is not collapsed until the macro is used in a regular
104           entry.
105
106           This function calls "bt_add_macro_text()", so the same proviso
107           about redefining old macros applies---a warning will be issued, and
108           the old value lost.
109
110       bt_delete_macro ()
111              void bt_delete_macro (char * macro);
112
113           Deletes a macro from the macro table.  If "macro" isn't defined,
114           takes no action.
115
116       bt_delete_all_macros ()
117              void bt_delete_all_macros (void);
118
119           Deletes all macros from the macro table.
120
121       bt_macro_length ()
122              int bt_macro_length (char *macro);
123
124           Returns the length of a macro's expansion text.  If the macro is
125           undefined, returns 0; no warning is issued.
126
127       bt_macro_text ()
128              char * bt_macro_text (char * macro,
129                                    char * filename,
130                                    int line);
131
132           Returns the expansion text of a macro.  If the macro is not
133           defined, issues a warning and returns "NULL".  "filename" and
134           "line" are used for generating this warning; if they don't apply
135           (i.e. you're not expanding the macro as a result of finding it in
136           some file), supply "NULL" for "filename" and 0 for "line".
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SEE ALSO

139       btparse
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AUTHOR

142       Greg Ward <gward@python.net>
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146btparse, version 0.88             2021-07-23                      BT_MACROS(1)
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