stringi (version 1.3.1)

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, literal, multiline,
  unix_lines, uword, error_on_unknown_escapes, ...)

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)]

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)]

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 http://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

...

any other arguments to this function are purposely ignored

Value

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

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, http://www.icu-project.org/apiref/icu4c/uregex_8h.html

Regular Expressions -- ICU User Guide, http://userguide.icu-project.org/strings/regexp

See Also

Other search_regex: stringi-search-regex, stringi-search

Examples

# NOT RUN {
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
# }