On this page:
alpha-char-p
char
char<
char<=
char>
char>=
char-code
char-downcase
char-equal
char-upcase
characterp
code-char
digit-char-p
digit-to-char
lower-case-p
standard-char-p
upper-case-p
1.4.4 Characters

procedure

(alpha-char-p x)  t

  x : (characterp x)
Determines whether x is an alphabetic character.

Examples:

> (alpha-char-p #\a)

't

> (alpha-char-p #\3)

'()

procedure

(char str n)  t

  str : (stringp str)
  n : (and (integerp n) (>= n 0) (< n (length str)))
Extracts the character at the nth (0-based) position in the string str.

Examples:

> (char "hello" 0)

#\h

> (char "hello" 4)

#\o

procedure

(char< x y)  t

  x : (characterp x)
  y : (characterp y)
Determines whether the character code of x is less than that of y.

Examples:

> (char< #\a #\b)

't

> (char< #\b #\a)

'()

> (char< #\b #\b)

'()

> (char< #\A #\a)

't

procedure

(char<= x y)  t

  x : (characterp x)
  y : (characterp y)
Determines whether the character code of x is less than or equal to that of y.

Examples:

> (char<= #\a #\b)

't

> (char<= #\b #\a)

'()

> (char<= #\b #\b)

't

> (char<= #\A #\a)

't

procedure

(char> x y)  t

  x : (characterp x)
  y : (characterp y)
Determines whether the character code of x is greater than that of y.

Examples:

> (char> #\a #\b)

'()

> (char> #\b #\a)

't

> (char> #\b #\b)

'()

> (char> #\A #\a)

'()

procedure

(char>= x y)  t

  x : (characterp x)
  y : (characterp y)
Determines whether the character code of x is greater than or equal to that of y.

Examples:

> (char>= #\a #\b)

'()

> (char>= #\b #\a)

't

> (char>= #\b #\b)

't

> (char>= #\A #\a)

'()

procedure

(char-code char)  t

  char : (characterp char)
Returns the numeric code for the given character.

Examples:

> (char-code #\a)

97

> (char-code #\Z)

90

procedure

(char-downcase char)  t

  char : (and (characterp char) (standard-char-p str))
Converts the given character to lowercase

Examples:

> (char-downcase #\A)

#\a

> (char-downcase #\a)

#\a

procedure

(char-equal x y)  t

  x : (and (characterp x) (standard-char-p x))
  y : (and (characterp y) (standard-char-p y))
Checks if the given characters are equal, ignoring to case.

Examples:

> (char-equal #\a #\a)

't

> (char-equal #\A #\a)

't

procedure

(char-upcase char)  t

  char : (and (characterp char) (standard-char-p str))
Converts the given character to uppercase

Examples:

> (char-upcase #\A)

#\A

> (char-upcase #\a)

#\A

procedure

(characterp x)  t

  x : t

Examples:

> (characterp #\a)

't

> (characterp "a")

'()

procedure

(code-char x)  t

  x : (and (integerp x) (>= x 0) (< x 256))
Converts the given number into its character equivalent.

Examples:

> (code-char 0)

#\nul

> (code-char 97)

#\a

> (code-char 255)

#\ÿ

> (code-char 1000)

#\Ϩ

procedure

(digit-char-p x)  t

  x : (characterp x)
Determines whether the given character represents a numerical digit.

Examples:

> (digit-char-p #\3)

3

> (digit-char-p #\a)

'()

procedure

(digit-to-char n)  t

  n : (and (integerp n) (<= 0 n) (>= 15 n))
Converts the given number into its equivalent character in hex notation.

Examples:

> (digit-to-char 7)

#\7

> (digit-to-char 10)

#\A

> (digit-to-char 15)

#\F

procedure

(lower-case-p x)  t

  x : (and (characterp x) (standard-char-p x))
Determines if x is a lowercase alphabetic character.

Examples:

> (lower-case-p #\a)

't

> (lower-case-p #\A)

'()

procedure

(standard-char-p x)  t

  x : (characterp x)
Checks if the given character is a member of the *standard-chars*. This includes the standard punctuation and alphanumeric characters, along with #\newline and #\space.

Examples:

> (standard-char-p #\a)

't

> (standard-char-p #\5)

't

> (standard-char-p #\tab)

'()

procedure

(upper-case-p x)  t

  x : (and (characterp x) (standard-char-p x))
Determines if x is an upper-case alphabetic character.

Examples:

> (upper-case-p #\A)

't

> (upper-case-p #\a)

'()