2.4.4 Characters

(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)

()

> (alpha-char-p 5)

Dracula program broke the contract (-> char? any) on here;

expected <char?>, given: 5

(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

> (char "hello" 100)

()

> (char 'symbol 3)

length: expects argument of type <proper list>; given symbol

(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

> (char< 5 10)

Dracula program broke the contract (-> char? char? any) on

here; expected <char?>, given: 5

(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

> (char<= 5 10)

Dracula program broke the contract (-> char? char? any) on

here; expected <char?>, given: 5

(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)

()

> (char> 5 10)

Dracula program broke the contract (-> char? char? any) on

here; expected <char?>, given: 5

(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)

()

> (char>= 5 10)

Dracula program broke the contract (-> char? char? any) on

here; expected <char?>, given: 5

(char-code char) → t

char : (characterp char)

Returns the numeric code for the given character.

Examples:

> (char-code #\a)

97

> (char-code #\Z)

90

> (char-code 'symbol)

Dracula program broke the contract (-> char? any) on here;

expected <char?>, given: symbol

(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

> (char-downcase 'symbol)

char-downcase: expects argument of type <character>; given

symbol

(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

> (char-equal 'a #\a)

Dracula program broke the contract (-> char? char? any) on

here; expected <char?>, given: a

(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

> (char-upcase 'symbol)

char-upcase: expects argument of type <character>; given

symbol

(characterp x)

Examples:

> (characterp #\a)

t

> (characterp "a")

()

(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

> (code-char #\5)

Dracula program broke the contract (-> integer? any) on

here; expected <integer?>, given: #\5

(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)

()

> (digit-char-p 'symbol)

Dracula program broke the contract (case-> (-> char?

any) (-> char? (integer-in 2 36) any)) on here; expected

<char?>, given: symbol

(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

> (digit-to-char #\7)

number->string: expects type <number> as 1st argument,

given: #\7; other arguments were: 16

(lower-case-p [x (and (characterp x) (standard-char-p x))])

#<procedure:t>Determines if x is a lowercase alphabetic character.

Examples:

> (lower-case-p #\a)

t

> (lower-case-p #\A)

()

> (lower-case-p 5)

Dracula program broke the contract (-> char? any) on here;

expected <char?>, given: 5

(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)

reference to undefined identifier: standard-char-p

> (standard-char-p #\5)

reference to undefined identifier: standard-char-p

> (standard-char-p 5)

reference to undefined identifier: standard-char-p

(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)

()

> (upper-case-p 5)

Dracula program broke the contract (-> char? any) on here;

expected <char?>, given: 5