String searching facilities described here
provide a way to locate a specific sequence of bytes in a string.
The search engine's settings may be tuned up (for example
to perform case-insensitive search) via a call to the
stri_opts_fixed function.
The fast Knuth-Morris-Pratt search algorithm, with worst time complexity of
O(n+p) (n == length(str), p == length(pattern))
is implemented (with some tweaks for very short search patterns).
Be aware that, for natural language processing, fixed pattern searching might not be what you actually require. It is because a bitwise match will not give correct results in cases of:
accented letters;
conjoined letters;
ignorable punctuation;
ignorable case,
see also about_search_coll.
Note that the conversion of input data to Unicode is done as usual.
Other search_fixed:
about_search,
stri_opts_fixed()
Other stringi_general_topics:
about_arguments,
about_encoding,
about_locale,
about_search_boundaries,
about_search_charclass,
about_search_coll,
about_search_regex,
about_search,
about_stringi