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Some of the procedures that operate on characters or strings ignore the
difference between upper case and lower case. These procedures have
-ci
(for “case insensitive”) embedded in their names.
These procedures take a character argument and return a character result.
If the argument is an upper–case or title–case character, and if there
is a single character that is its lower–case form, then
char-downcase
returns that character.
If the argument is a lower–case or title–case character, and there is
a single character that is its upper–case form, then char-upcase
returns that character.
If the argument is a lower–case or upper–case character, and there is
a single character that is its title–case form, then
char-titlecase
returns that character.
If the argument is not a title–case character and there is no single
character that is its title–case form, then char-titlecase
returns the upper–case form of the argument.
Finally, if the character has a case–folded character, then
char-foldcase
returns that character. Otherwise the character
returned is the same as the argument.
For Turkic characters #\x130
and #\x131
,
char-foldcase
behaves as the identity function; otherwise
char-foldcase
is the same as char-downcase
composed with
char-upcase
.
(char-upcase #\i) ⇒ #\I (char-downcase #\i) ⇒ #\i (char-titlecase #\i) ⇒ #\I (char-foldcase #\i) ⇒ #\i (char-upcase #\ß) ⇒ #\ß (char-downcase #\ß) ⇒ #\ß (char-titlecase #\ß) ⇒ #\ß (char-foldcase #\ß) ⇒ #\ß (char-upcase #\Σ) ⇒ #\Σ (char-downcase #\Σ) ⇒ #\σ (char-titlecase #\Σ) ⇒ #\Σ (char-foldcase #\Σ) ⇒ #\σ (char-upcase #\ς) ⇒ #\Σ (char-downcase #\ς) ⇒ #\ς (char-titlecase #\ς) ⇒ #\Σ (char-foldcase #\ς) ⇒ #\σ
Note:
char-titlecase
does not always return a title–case character.
Note: These procedures are consistent with Unicode’s locale–independent mappings from scalar values to scalar values for upcase, downcase, titlecase, and case–folding operations. These mappings can be extracted from UnicodeData.txt and CaseFolding.txt from the Unicode Consortium, ignoring Turkic mappings in the latter.
Note that these character–based procedures are an incomplete approximation to case conversion, even ignoring the user’s locale. In general, case mappings require the context of a string, both in arguments and in result. The
string-upcase
,string-downcase
,string-titlecase
, andstring-foldcase
procedures perform more general case conversion.
These procedures are similar to char=?
, etc., but operate on the
case–folded versions of the characters.
(char-ci<? #\z #\Z) ⇒ #f (char-ci=? #\z #\Z) ⇒ #f (char-ci=? #\ς #\σ) ⇒ #t
These procedures return #t
if their arguments are alphabetic,
numeric, whitespace, upper–case, lower–case, or title–case
characters, respectively; otherwise they return #f
.
A character is alphabetic if it has the Unicode “Alphabetic” property. A character is numeric if it has the Unicode “Numeric” property. A character is whitespace if has the Unicode “White_Space” property. A character is upper case if it has the Unicode “Uppercase” property, lower case if it has the “Lowercase” property, and title case if it is in the Lt general category.
(char-alphabetic? #\a) ⇒ #t (char-numeric? #\1) ⇒ #t (char-whitespace? #\space) ⇒ #t (char-whitespace? #\x00A0) ⇒ #t (char-upper-case? #\Σ) ⇒ #t (char-lower-case? #\σ) ⇒ #t (char-lower-case? #\x00AA) ⇒ #t (char-title-case? #\I) ⇒ #f (char-title-case? #\x01C5) ⇒ #t
Return a symbol representing the Unicode general category of
char, one of 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
.
(char-general-category #\a) ⇒ Ll (char-general-category #\space) ⇒ Zs (char-general-category #\x10FFFF) ⇒ Cn
The following functions are deprecated; they really don’t and cannot do the right thing, because in some languages upper and lower case can use different number of characters.
Deprecated: Destructively modify str, replacing the letters by their upper-case equivalents.
Deprecated: Destructively modify str, replacing the letters by their upper-lower equivalents.
Deprecated: Destructively modify str, such that the letters that start a new word are replaced by their title-case equivalents, while non-initial letters are replaced by their lower-case equivalents.
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