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RE/flex supports Unicode regular expression patterns in lexer specifications and automatically tokenizes UTF-8, UTF-16, and UTF-32 input files. Code pages may be specified to tokenize input files encoded in ISO/IEC 8859 1 to 16, Windows-1250 to Windows-1258, CP-437, CP-850, CP-858, MacRoman, KOI-8, EBCDIC, and so on. Normalization to UTF-8 is ...
A regular expression (shortened as regex or regexp), [1] sometimes referred to as rational expression, [2] [3] is a sequence of characters that specifies a match pattern in text. Usually such patterns are used by string-searching algorithms for "find" or "find and replace" operations on strings , or for input validation .
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C++ Qt GNU GPL v. 3.0, Qt GNU LGPL v. 2.1, Qt Commercial. Kate, Kile: regex - Henry Spencer's regular expression libraries ArgList: C BSD RE2: RE2: C++ BSD Go, Google Sheets, Gmail, G Suite Henry Spencer's Advanced Regular Expressions Tcl: C BSD RGX RGX : C++ based component library P6R RXP Titan IC: RTL Proprietary
Here is a very simple program in re2c (example.re). It checks that all input arguments are hexadecimal numbers. The code for re2c is enclosed in comments /*!re2c ... */, all the rest is plain C code. See the official re2c website for more complex examples. [23]
A parsing expression is a kind of pattern that each string may either match or not match.In case of a match, there is a unique prefix of the string (which may be the whole string, the empty string, or something in between) which has been consumed by the parsing expression; this prefix is what one would usually think of as having matched the expression.
RE2 is a software library which implements a regular expression engine. It uses finite-state machines, in contrast to most other regular expression libraries. RE2 supports a C++ interface. RE2 was implemented by Google and Google uses RE2 for Google products. [3]
Regular languages are a category of languages (sometimes termed Chomsky Type 3) which can be matched by a state machine (more specifically, by a deterministic finite automaton or a nondeterministic finite automaton) constructed from a regular expression. In particular, a regular language can match constructs like "A follows B", "Either A or B ...