casefuns: Unicode Case Conversions

In Unicode: Unicode Data and Utilities

Unicode Case Conversions

Description

Default Unicode algorithms for case conversion.

Usage

u_to_lower_case(x)
u_to_upper_case(x)
u_to_title_case(x)
u_case_fold(x)

Arguments

x	R objects (see Details).

Details

These functions are generic functions, with methods for the Unicode character classes (u_char, u_char_range, and u_char_seq) which suitably apply the case mappings to the Unicode characters given by x, and a default method which treats x as a vector of “Unicode strings”, and returns a vector of UTF-8 encoded character strings with the results of the case conversion of the elements of x.

Currently, only the unconditional case maps are available for conversion to lower, upper or title case: other variants may be added eventually.

Currently, conversion to title case is only available for u_char objects. Other methods will be added eventually (once the Unicode text segmentation algorithm is implemented for detecting word boundaries).

Currently, u_case_fold only performs full case folding using the Unicode case mappings with status “C” and “F”: other variants will be added eventually.

Value

For the methods for the Unicode character classes, a u_char_seq vector of Unicode character sequences with the conversions of the characters in x.

For the default method, a UTF-8 encoded character string with the results of the case conversions of the elements of x.

Examples

## Latin upper case letters A to Z:
x <- as.u_char(as.u_char_range("0041..005A"))
## In case we did not know the code points, we could use e.g.
x <- as.u_char(utf8ToInt(paste(LETTERS, collapse = "")))
vapply(x, intToUtf8, "")
## Unicode character method:
vapply(u_to_lower_case(x), intToUtf8, "")
## Default method:
u_to_lower_case(LETTERS)

u_case_fold("Hi Dave.")

## More interesting stuff: sharp s.
u_to_upper_case("heiß")
## Note that the default full upper case mapping of U+00DF (LATIN SMALL
## LETTER SHARP S) is *not* to U+1E9E (LATIN CAPITAL LETTER SHARP S).
u_case_fold("heiß")

Unicode documentation built on Sept. 30, 2022, 9:06 a.m.