stringi (version 1.7.8)

stri_opts_regex: Generate a List with Regex Matcher Settings

Description

A convenience function to tune the ICU regular expressions matcher's behavior, e.g., in stri_count_regex and other stringi-search-regex functions.

Usage

stri_opts_regex(
  case_insensitive,
  comments,
  dotall,
  dot_all = dotall,
  literal,
  multiline,
  multi_line = multiline,
  unix_lines,
  uword,
  error_on_unknown_escapes,
  time_limit = 0L,
  stack_limit = 0L,
  ...
)

Value

Returns a named list object; missing settings are left with default values.

Arguments

case_insensitive

logical; enables case insensitive matching [regex flag (?i)]

comments

logical; allows white space and comments within patterns [regex flag (?x)]

dotall

logical; if set, `.` matches line terminators, otherwise matching of `.` stops at a line end [regex flag (?s)]

dot_all

alias of dotall

literal

logical; if set, treat the entire pattern as a literal string: metacharacters or escape sequences in the input sequence will be given no special meaning; note that in most cases you would rather use the stringi-search-fixed facilities in this case

multiline

logical; controls the behavior of `$` and `^`. If set, recognize line terminators within a string, otherwise, match only at start and end of input string [regex flag (?m)]

multi_line

alias of multiline

unix_lines

logical; Unix-only line endings; when enabled, only U+000a is recognized as a line ending by `.`, `$`, and `^`.

uword

logical; Unicode word boundaries; if set, uses the Unicode TR 29 definition of word boundaries; warning: Unicode word boundaries are quite different from traditional regex word boundaries. [regex flag (?w)] See https://unicode.org/reports/tr29/#Word_Boundaries

error_on_unknown_escapes

logical; whether to generate an error on unrecognized backslash escapes; if set, fail with an error on patterns that contain backslash-escaped ASCII letters without a known special meaning; otherwise, these escaped letters represent themselves

time_limit

integer; processing time limit, in ~milliseconds (but not precisely so, depends on the CPU speed), for match operations; setting a limit is desirable if poorly written regexes are expected on input; 0 for no limit

stack_limit

integer; maximal size, in bytes, of the heap storage available for the match backtracking stack; setting a limit is desirable if poorly written regexes are expected on input; 0 for no limit

...

[DEPRECATED] any other arguments passed to this function generate a warning; this argument will be removed in the future

Author

Marek Gagolewski and other contributors

Details

Note that some regex settings may be changed using ICU regex flags inside regexes. For example, '(?i)pattern' performs a case-insensitive match of a given pattern, see the ICU User Guide entry on Regular Expressions in the References section or stringi-search-regex.

References

enum URegexpFlag: Constants for Regular Expression Match Modes -- ICU4C API Documentation, https://unicode-org.github.io/icu-docs/apidoc/dev/icu4c/uregex_8h.html

Regular Expressions -- ICU User Guide, https://unicode-org.github.io/icu/userguide/strings/regexp.html

See Also

The official online manual of stringi at https://stringi.gagolewski.com/

Gagolewski M., stringi: Fast and portable character string processing in R, Journal of Statistical Software 103(2), 2022, 1-59, tools:::Rd_expr_doi("10.18637/jss.v103.i02")

Other search_regex: about_search_regex, about_search

Examples

stri_detect_regex('ala', 'ALA') # case-sensitive by default
stri_detect_regex('ala', 'ALA', opts_regex=stri_opts_regex(case_insensitive=TRUE))
stri_detect_regex('ala', 'ALA', case_insensitive=TRUE) # equivalent
stri_detect_regex('ala', '(?i)ALA') # equivalent