CLHS: Function CHAR=, CHAR/=, CHAR<, CHAR>...

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Function CHAR=, CHAR/=, CHAR<, CHAR>, CHAR<=, CHAR>=, CHAR-EQUAL, CHAR-NOT-EQUAL, CHAR-LESSP, CHAR-GREATERP, CHAR-NOT-GREATERP, CHAR-NOT-LESSP

Syntax:

char= `&rest` characters+ => generalized-boolean

char/= `&rest` characters+ => generalized-boolean

char< `&rest` characters+ => generalized-boolean

char> `&rest` characters+ => generalized-boolean

char<= `&rest` characters+ => generalized-boolean

char>= `&rest` characters+ => generalized-boolean

char-equal `&rest` characters+ => generalized-boolean

char-not-equal `&rest` characters+ => generalized-boolean

char-lessp `&rest` characters+ => generalized-boolean

char-greaterp `&rest` characters+ => generalized-boolean

char-not-greaterp `&rest` characters+ => generalized-boolean

char-not-lessp `&rest` characters+ => generalized-boolean

Arguments and Values:

character---a character.

generalized-boolean---a generalized boolean.

Description:

These predicates compare characters.

char= returns true if all characters are the same; otherwise, it returns false. If two characters differ in any implementation-defined attributes, then they are not char=.

char/= returns true if all characters are different; otherwise, it returns false.

char< returns true if the characters are monotonically increasing; otherwise, it returns false. If two characters have identical implementation-defined attributes, then their ordering by char< is consistent with the numerical ordering by the predicate `<` on their codes.

char> returns true if the characters are monotonically decreasing; otherwise, it returns false. If two characters have identical implementation-defined attributes, then their ordering by char> is consistent with the numerical ordering by the predicate `>` on their codes.

char<= returns true if the characters are monotonically nondecreasing; otherwise, it returns false. If two characters have identical implementation-defined attributes, then their ordering by char<= is consistent with the numerical ordering by the predicate `<=` on their codes.

char>= returns true if the characters are monotonically nonincreasing; otherwise, it returns false. If two characters have identical implementation-defined attributes, then their ordering by char>= is consistent with the numerical ordering by the predicate `>=` on their codes.

char-equal, char-not-equal, char-lessp, char-greaterp, char-not-greaterp, and char-not-lessp are similar to char=, char/=, char<, char>, char<=, char>=, respectively, except that they ignore differences in case and might have an implementation-defined behavior for non-simple characters. For example, an implementation might define that char-equal, etc. ignore certain implementation-defined attributes. The effect, if any, of each implementation-defined attribute upon these functions must be specified as part of the definition of that attribute.

Examples:

     (char= #\d #\d) =>  true
     (char= #\A #\a) =>  false
     (char= #\d #\x) =>  false
     (char= #\d #\D) =>  false
     (char/= #\d #\d) =>  false
     (char/= #\d #\x) =>  true
     (char/= #\d #\D) =>  true
     (char= #\d #\d #\d #\d) =>  true
     (char/= #\d #\d #\d #\d) =>  false
     (char= #\d #\d #\x #\d) =>  false
     (char/= #\d #\d #\x #\d) =>  false
     (char= #\d #\y #\x #\c) =>  false
     (char/= #\d #\y #\x #\c) =>  true
     (char= #\d #\c #\d) =>  false
     (char/= #\d #\c #\d) =>  false
     (char< #\d #\x) =>  true
     (char<= #\d #\x) =>  true
     (char< #\d #\d) =>  false
     (char<= #\d #\d) =>  true
     (char< #\a #\e #\y #\z) =>  true
     (char<= #\a #\e #\y #\z) =>  true
     (char< #\a #\e #\e #\y) =>  false
     (char<= #\a #\e #\e #\y) =>  true
     (char> #\e #\d) =>  true
     (char>= #\e #\d) =>  true
     (char> #\d #\c #\b #\a) =>  true
     (char>= #\d #\c #\b #\a) =>  true
     (char> #\d #\d #\c #\a) =>  false
     (char>= #\d #\d #\c #\a) =>  true
     (char> #\e #\d #\b #\c #\a) =>  false
     (char>= #\e #\d #\b #\c #\a) =>  false
     (char> #\z #\A) =>  implementation-dependent
     (char> #\Z #\a) =>  implementation-dependent
     (char-equal #\A #\a) =>  true
     (stable-sort (list #\b #\A #\B #\a #\c #\C) #'char-lessp)
    =>  (#\A #\a #\b #\B #\c #\C)
     (stable-sort (list #\b #\A #\B #\a #\c #\C) #'char<)
    =>  (#\A #\B #\C #\a #\b #\c) ;Implementation A
    =>  (#\a #\b #\c #\A #\B #\C) ;Implementation B
    =>  (#\a #\A #\b #\B #\c #\C) ;Implementation C
    =>  (#\A #\a #\B #\b #\C #\c) ;Implementation D
    =>  (#\A #\B #\a #\b #\C #\c) ;Implementation E

Affected By: None.

Exceptional Situations:

Should signal an error of type program-error if at least one character is not supplied.

See Also:

Section 2.1 (Character Syntax), Section 13.1.10 (Documentation of Implementation-Defined Scripts)

Notes:

If characters differ in their code attribute or any implementation-defined attribute, they are considered to be different by char=.

There is no requirement that `(eq c1 c2)` be true merely because `(char= c1 c2)` is true. While eq can distinguish two characters that char= does not, it is distinguishing them not as characters, but in some sense on the basis of a lower level implementation characteristic. If `(eq c1 c2)` is true, then `(char= c1 c2)` is also true. eql and equal compare characters in the same way that char= does.

The manner in which case is used by char-equal, char-not-equal, char-lessp, char-greaterp, char-not-greaterp, and char-not-lessp implies an ordering for standard characters such that `A=a`, `B=b`, and so on, up to `Z=z`, and furthermore either `9<A` or `Z<0`.

The following X3J13 cleanup issue, not part of the specification, applies to this section:

- CHARACTER-PROPOSAL:2-1-1

Copyright 1996-2005, LispWorks Ltd. All rights reserved.