stri_width: Determine the Width of Code Points

Description

Approximates the number of text columns the ‘cat()’ function should use to print a string with a mono-spaced font.

Usage

stri_width(str)

Arguments

str	character vector or an object coercible to

Details

The Unicode standard does not formalize the notion of a character width. Roughly based on https://www.cl.cam.ac.uk/~mgk25/ucs/wcwidth.c and the UAX #11 we proceed as follows. The following code points are of width 0:

• code points with general category (see stringi-search-charclass) Me, Mn, and Cf),

• C0 and C1 control codes (general category Cc) - for compatibility with the nchar function,

• Hangul Jamo medial vowels and final consonants (code points with enumerable property UCHAR_HANGUL_SYLLABLE_TYPE equal to U_HST_VOWEL_JAMO or U_HST_TRAILING_JAMO; note that applying the NFC normalization with stri_trans_nfc is encouraged),

• ZERO WIDTH SPACE (U+200B),

Characters with the UCHAR_EAST_ASIAN_WIDTH enumerable property equal to U_EA_FULLWIDTH or U_EA_WIDE are of width 2. SOFT HYPHEN (U+00AD) (for compatibility with nchar) as well as any other characters have width 1.

Value

Returns an integer vector of the same length as str.

References

East Asian Width – Unicode Standard Annex #11, https://www.unicode.org/reports/tr11/

See Also

Other length: stri_isempty(), stri_length(), stri_numbytes()

Examples

stri_width(LETTERS[1:5])
stri_width(stri_trans_nfkd('\u0105'))
stri_width( # Full-width equivalents of ASCII characters:
   stri_enc_fromutf32(as.list(c(0x3000, 0xFF01:0xFF5E)))
)
stri_width(stri_trans_nfkd('\ubc1f')) # includes Hangul Jamo medial vowels and final consonants