3.5 Characters
Characters in Guide: Racket introduces characters.
Characters range over Unicode scalar values, which includes characters whose values range from #x0 to #x10FFFF, but not including #xD800 to #xDFFF. The scalar values are a subset of the Unicode code points.
Two characters are eqv? if they correspond to the same scalar value. For each scalar value less than 256, character values that are eqv? are also eq?.
3.5.1 Characters and Scalar Values
Return #t if v is a character, #f
otherwise.
| (char->integer char) → exact-integer? |
| char : char? |
Returns a character’s code-point number.
Example: |
| > (char->integer #\A) |
65 |
| (integer->char k) → char? | |||||||||
|
Return the character whose code-point number is k. For
k less than 256, the result is the same object for
the same k.
Example: |
| > (integer->char 65) |
#\A |
| (char-utf-8-length char) → (integer-in 1 6) |
| char : char? |
3.5.2 Character Comparisons
Returns #t if all of the arguments are eqv?.
Examples: |
| > (char=? #\a #\a) |
#t |
| > (char=? #\a #\A #\a) |
#f |
Returns #t if the arguments are sorted increasing, where
two characters are ordered by their scalar values, #f
otherwise.
Examples: |
| > (char<? #\A #\a) |
#t |
| > (char<? #\a #\A) |
#f |
| > (char<? #\a #\b #\c) |
#t |
Like char<?, but checks whether the arguments are nondecreasing.
Examples: |
| > (char<=? #\A #\a) |
#t |
| > (char<=? #\a #\A) |
#f |
| > (char<=? #\a #\b #\b) |
#t |
Like char<?, but checks whether the arguments are decreasing.
Examples: |
| > (char>? #\A #\a) |
#f |
| > (char>? #\a #\A) |
#t |
| > (char>? #\c #\b #\a) |
#t |
Like char<?, but checks whether the arguments are nonincreasing.
Examples: |
| > (char>=? #\A #\a) |
#f |
| > (char>=? #\a #\A) |
#t |
| > (char>=? #\c #\b #\b) |
#t |
Returns #t if all of the arguments are eqv? after
locale-insensitive case-folding via char-foldcase.
Examples: |
| > (char-ci=? #\A #\a) |
#t |
| > (char-ci=? #\a #\a #\a) |
#t |
Like char<?, but checks whether the arguments would be in
increasing order if each was first case-folded using
char-foldcase (which is locale-insensitive).
Examples: |
| > (char-ci<? #\A #\a) |
#f |
| > (char-ci<? #\a #\b) |
#t |
| > (char-ci<? #\a #\b #\c) |
#t |
| (char-ci<=? char1 char2 ...+) → boolean? |
| char1 : char? |
| char2 : char? |
Like char-ci<?, but checks whether the arguments would be nondecreasing after case-folding.
Examples: |
| > (char-ci<=? #\A #\a) |
#t |
| > (char-ci<=? #\a #\A) |
#t |
| > (char-ci<=? #\a #\b #\b) |
#t |
Like char-ci<?, but checks whether the arguments would be decreasing after case-folding.
Examples: |
| > (char-ci>? #\A #\a) |
#f |
| > (char-ci>? #\b #\A) |
#t |
| > (char-ci>? #\c #\b #\a) |
#t |
| (char-ci>=? char1 char2 ...+) → boolean? |
| char1 : char? |
| char2 : char? |
Like char-ci<?, but checks whether the arguments would be nonincreasing after case-folding.
Examples: |
| > (char-ci>=? #\A #\a) |
#t |
| > (char-ci>=? #\a #\A) |
#t |
| > (char-ci>=? #\c #\b #\b) |
#t |
3.5.3 Classifications
| (char-alphabetic? char) → boolean? |
| char : char? |
Returns #t if char has the Unicode “Alphabetic”
property.
| (char-lower-case? char) → boolean? |
| char : char? |
Returns #t if char has the Unicode “Lowercase”
property.
| (char-upper-case? char) → boolean? |
| char : char? |
Returns #t if char has the Unicode “Uppercase”
property.
| (char-title-case? char) → boolean? |
| char : char? |
Returns #t if char’s Unicode general category is
Lt, #f otherwise.
| (char-numeric? char) → boolean? |
| char : char? |
Returns #t if char has the Unicode “Numeric”
property.
| (char-symbolic? char) → boolean? |
| char : char? |
Returns #t if char’s Unicode general category is
Sm, Sc, Sk, or So, #f otherwise.
| (char-punctuation? char) → boolean? |
| char : char? |
Returns #t if char’s Unicode general category is
Pc, Pd, Ps, Pe, Pi, Pf, or
Po, #f otherwise.
| (char-graphic? char) → boolean? |
| char : char? |
Returns #t if char’s Unicode general category is
Mn, Mc, Me, or if one of the following produces
#t when applied to char: char-alphabetic?,
char-numeric?, char-symbolic?, or
char-punctuation?.
| (char-whitespace? char) → boolean? |
| char : char? |
Returns #t if char has the Unicode “White_Space”
property.
| (char-blank? char) → boolean? |
| char : char? |
Returns #t if char’s Unicode general category is
Zs or if char is #\tab. (These correspond to
horizontal whitespace.)
| (char-iso-control? char) → boolean? |
| char : char? |
Return #t if char is between #\nul and
#\u001F inclusive or #\rubout and #\u009F
inclusive.
| (char-general-category char) → symbol? |
| char : char? |
Returns a symbol representing the character’s Unicode general
category, which is 'lu, 'll,
'lt, 'lm, 'lo,
'mn, 'mc, 'me,
'nd, 'nl, 'no,
'ps, 'pe, 'pi,
'pf, 'pd, 'pc,
'po, 'sc, 'sm,
'sk, 'so, 'zs,
'zp, 'zl, 'cc,
'cf, 'cs, 'co, or
'cn.
| (make-known-char-range-list) | |||||||
|
Produces a list of three-element lists, where each three-element list
represents a set of consecutive code points for which the Unicode
standard specifies character properties. Each three-element list
contains two integers and a boolean; the first integer is a starting
code-point value (inclusive), the second integer is an ending
code-point value (inclusive), and the boolean is #t when all
characters in the code-point range have identical results for all of
the character predicates above. The three-element lists are ordered in
the overall result list such that later lists represent larger
code-point values, and all three-element lists are separated from
every other by at least one code-point value that is not specified by
Unicode.
3.5.4 Character Conversions
| (char-upcase char) → char? |
| char : char? |
Produces a character consistent with the 1-to-1 code point mapping
defined by Unicode. If char has no upcase mapping,
char-upcase produces char.
String procedures, such as string-upcase, handle the case where Unicode defines a locale-independent mapping from the code point to a code-point sequence (in addition to the 1-1 mapping on scalar values).
Examples: |
| > (char-upcase #\a) |
#\A |
| > (char-upcase #\λ) |
#\Λ |
| > (char-upcase #\space) |
#\space |
| (char-downcase char) → char? |
| char : char? |
Like char-upcase, but for the Unicode downcase mapping.
Examples: |
| > (char-downcase #\A) |
#\a |
| > (char-downcase #\Λ) |
#\λ |
| > (char-downcase #\space) |
#\space |
| (char-titlecase char) → char? |
| char : char? |
Like char-upcase, but for the Unicode titlecase mapping.
Examples: |
| > (char-upcase #\a) |
#\A |
| > (char-upcase #\λ) |
#\Λ |
| > (char-upcase #\space) |
#\space |
| (char-foldcase char) → char? |
| char : char? |
Like char-upcase, but for the Unicode case-folding mapping.
Examples: |
| > (char-foldcase #\A) |
#\a |
| > (char-foldcase #\Σ) |
#\σ |
| > (char-foldcase #\ς) |
#\σ |
| > (char-foldcase #\space) |
#\space |