rebus.base (version 0.0-3)

repeated: Repeat values

Description

Match repeated values.

Usage

repeated(x, lo, hi, lazy = FALSE, char_class = NA)
optional(x, char_class = NA)
lazy(x)
zero_or_more(x, char_class = NA)
one_or_more(x, char_class = NA)

Arguments

x

A character vector.

lo

A non-negative integer. Minimum number of repeats, when grouped.

hi

positive integer. Maximum number of repeats, when grouped.

lazy

A logical value. Should repetition be matched lazily or greedily?

char_class

A logical value. Should x be wrapped in a character class? If NA, the function guesses whether that's a good idea.

Value

A character vector representing part or all of a regular expression.

References

http://www.regular-expressions.info/repeat.html and http://www.rexegg.com/regex-quantifiers.html

Examples

# Can match constants or class values
repeated(GRAPH, 2, 5)
repeated(graph(), 2, 5)   # same

# Short cuts for special cases
optional(blank())         # same as repeated(blank(), 0, 1)
zero_or_more(hex_digit()) # same as repeated(hex_digit(), 0, Inf)
one_or_more(printable())  # same as repeated(printable(), 1, Inf)

# 'Lazy' matching (match smallest no. of chars)
repeated(cntrl(), 2, 5, lazy = TRUE)
lazy(one_or_more(cntrl()))

# Overriding character class wrapping
repeated(ANY_CHAR, 2, 5, char_class = FALSE)

# Usage
x <- "1234567890"
stringi::stri_extract_first_regex(x, one_or_more(DIGIT))
stringi::stri_extract_first_regex(x, repeated(DIGIT, lo = 3, hi = 6))
stringi::stri_extract_first_regex(x, lazy(repeated(DIGIT, lo = 3, hi = 6)))

col <- c("color", "colour")
stringi::stri_detect_regex(col, "colo" %R% optional("u") %R% "r")

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