Hapy built-in rules provide convenience and safety for common use cases. All these rules are objects and functions declared in Hapy/Rules.cc. Text matching is case sensitive. Hapy rule expression syntax is documented elsewhere.
Besides rule semantics, the table below provides a semantically equivalent expression using non-terminals or other rules. The actual Hapy implementation of a built-in rule usually differs from its semantic equivalent.
| Built-in rule | Semantics | Semantically equivalent expression |
|---|---|---|
| anychar_r | matches any single character (byte, octet) | "\000" | "\001" | ... | "\377" |
| char_set_r(const string &set) | matches any single character in the user-specified set | set[0] | set[1] | ... | set[N] |
| char_range_r(char first, char last) | matches any single character in the user-specified inclusive range | first | (char)(first+1) | ... | last |
| alpha_r | matches any alphabetic character (see isalpha(3) man page) | "A" | "B" | ... "z" |
| digit_r | matches any decimal digit (see isdigit(3) man page) | "0" | "1" | ... "9" |
| alnum_r | matches any alphabetic character and any decimal digit (see isalnum(3) man page) | alpha_r | digit_r |
| space_r | matches any whitespace character, including tabulation and line termination characters (see isspace(3) man page). | " " | "\t" | "\r" | "\n" | ... |
| eol_r | matches the end of the line; currently that means a "\n" character; is there a better way? | "\n" |
| char_r(char c) | matches a given character | "<c>" |
| string_r(const string &s) | matches a given sequence of characters (string) | "<s>" |
| quoted_r(const Rule &element, const Rule &open, const Rule &close) | matches zero or more elements enclosed in opening and closing "quotes"; the opening and closing rules do not have to match; this is handy for comments, strings, CDATA, and other "enclosed" elements. | open >> *(element-close) >> close |
| empty_r | an always successful zero-size match; matches any input without advancing the input position | |
| end_r | matches the end of input; a zero-size match |