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
)

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

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.

Value¶

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

Author(s)¶

Marek Gagolewski and other contributors

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

Examples¶

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