diff options
| -rw-r--r-- | regex.c | 11 | ||||
| -rw-r--r-- | regex.h | 2 | ||||
| -rw-r--r-- | txr.1 | 72 |
3 files changed, 74 insertions, 11 deletions
@@ -1854,20 +1854,21 @@ val match_regex(val str, val reg, val pos) return nil; } -val match_regex_right(val str, val regex, val pos) +val match_regex_right(val str, val regex, val end) { + val pos = zero; val slen = length(str); - if (!pos) - pos = zero; + if (!end || gt(end, slen)) + end = slen; - for (;;) { + while (lt(pos, end)) { cons_bind (from, len, search_regex(str, regex, pos, nil)); if (!from) return nil; - if (eql(plus(from, len), slen)) + if (eql(plus(from, len), end)) return len; pos = plus(pos, one); @@ -31,7 +31,7 @@ val regex_compile(val regex, val error_stream); val regexp(val); val search_regex(val haystack, val needle_regex, val start_num, val from_end); val match_regex(val str, val regex, val pos); -val match_regex_right(val str, val regex, val pos); +val match_regex_right(val str, val regex, val end); val regsub(val regex, val repl, val str); void regex_init(void); @@ -9604,19 +9604,16 @@ and error. .SH REGULAR EXPRESSION LIBRARY -.SS Functions search-regex and match-regex +.SS Function search-regex .TP Syntax: (search-regex <haystack-string> <needle-regex> : <start> <from-end>) - (match-regex <string> <regex> : <position>) .TP Description -These functions perform regular-expression-based searching and matching. - The search-regex function searches through <haystack-string> starting at position <start> for a match for <needle-regex>. If <start> is omitted, the search starts at position 0. If <from-end> is specified, the search @@ -9625,11 +9622,76 @@ This function returns nil if no match is found, otherwise it returns a cons pair, whose car indicates the position of the match, and whose cdr indicates the length of the match. +.SS Function match-regex + +.TP +Syntax: + + (match-regex <string> <regex> : <position>) + +.TP +Description + The match-regex function tests whether <regex> matches at <position> in <string>. If <position> is not specified, it is taken to be zero. If the regex matches, then the length of the match is returned. If it does not match, then nil is returned. -. + +.SS Function match-regex-right + +.TP +Syntax: + + (match-regex-right <string> <regex> : <end-position>) + +.TP +Description + +The match-regex function tests whether <string> contains a match which ends +precisely on the character just before <end-position>. If <end-position> is +not specified, it defaults to the length of the string, and the function +performs a right-anchored regex match. + +If a match is found, then the length of the match is returned, and +the matching substring is then returned. + +The match must terminate just before <end-position> in the sense that +additional characters at <end-position> and beyond can no longer satisfy the +regular expression. More formally, the function searches, starting from +position zero, for positions where there occurs a match for the regular +expression, taking the longest possible match. The length of first such a match +which terminates on the character just before <end-position> is returned. +If no such a match is found, then nil is returned. + +.TP +Examples: + + ;; Return matching portion rather than length thereof. + + (defun match-regex-right-substring (str reg : end-pos) + (set end-pos (or end-pos (length str))) + (let ((len (match-regex-right str reg end-pos))) + (if len + [str (- end-pos len)..end-pos] + nil))) + + (match-regex-right-substring "abc" #/c/) -> "" + + (match-regex-right-substring "acc" #/c*/) -> "cc" + + ;; Regex matches starting at multiple positions, but all + ;; the matches extend past the limit. + (match-regex-right-substring "acc" #/c*/ 2) -> nil + + ;; If the above behavior is not wanted, then + ;; we can extract the string up to the limiting + ;; position and do the match on that. + (match-regex-right-substring ["acc" 0..2] #/c*/) -> "c" + + ;; Equivalent of above call + (match-regex-right-substring "ac" #/c*/) -> "c" + + .SS Function regsub .TP |