2.4.3 Strings

Some string functions can be found in the section on Sequences as well.

(make-character-list x) → character-listp

x : t

This function will coerce a value to a list of characters.

Examples:

> (make-character-list "hello")

()

(string x) → t

x : (or (stringp x) (symbolp x) (characterp x))

Uses coerce to convert the input into a string.

Examples:

> (string "abc")

"abc"

> (string 'abc)

"ABC"

> (string #\a)

"a"

> (string 123)

()

(string-append x y) → t

x : (stringp x)

y : (stringp y)

Concatenates two strings together.

Examples:

> (string-append "ab" "cd")

"abcd"

> (string-append 'ab "cd")

/Volumes/Maldis/Users/cce/plt/research/dracula/release/src/l

anguage/primitive-procedures/acl2-prims-scheme.scm:38:28:

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

(symbols ’string ’list) any) (->* ((symbols ’string

’list)) (or/c (listof string?) (listof

(listof any/c))) any)) on here; expected <(or/c (listof

string?) (listof (listof any/c)))>, given: (ab "cd")

> (string-append 5 "ab")

/Volumes/Maldis/Users/cce/plt/research/dracula/release/src/l

anguage/primitive-procedures/acl2-prims-scheme.scm:38:28:

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

(symbols ’string ’list) any) (->* ((symbols ’string

’list)) (or/c (listof string?) (listof

(listof any/c))) any)) on here; expected <(or/c (listof

string?) (listof (listof any/c)))>, given: (5 "ab")

(string-downcase str) → t

str : (and (stringp str) (standard-char-listp (coerce str 'list)))

Converts the characters in str to lowercase.

Examples:

> (string-downcase "ABCdef")

"abcdef"

> (string-downcase 'ABCdef)

string-downcase: expects argument of type <string>; given

ABCdef

> (string-downcase 12345)

string-downcase: expects argument of type <string>; given

12345

(string-equal x y) → t

x : (and (stringp x) (standard-char-listp (coerce x 'list)))

y : (and (stringp y) (standard-char-listp (coerce y 'list)))

Compares two strings to see if they are equal.

Examples:

> (string-equal "ab" "cd")

()

> (string-equal "ab" "ab")

t

(string-upcase str) → t

str : (and (stringp str) (standard-char-listp (coerce str 'list)))

Converts the characters in str to uppercase.

Examples:

> (string-upcase "ABCdef")

"ABCDEF"

> (string-upcase 'ABCdef)

string-upcase: expects argument of type <string>; given

ABCdef

> (string-upcase 12345)

string-upcase: expects argument of type <string>; given

12345

(string< x y) → t

x : (stringp x)

y : (stringp y)

Compares the two strings for lexicographical ordering. Returns non-nil if and only if x precedes y lexicographically. When non-nil, the number returned is the first position at which the strings differ.

Examples:

> (string< "ab" "cd")

0

> (string< "ab" "abc")

2

> (string< 'symbol "string")

/Volumes/Maldis/Users/cce/plt/research/dracula/release/src/l

anguage/checking-proc.scm:36:21: Dracula program broke the

contract (-> string? string? any) on here; expected

<string?>, given: symbol

(string<= x y) → t

x : (stringp x)

y : (stringp y)

Compares the two strings for lexicographical ordering. Returns non-nil if and only if x precedes y lexicographically. If they differ, the number returned is the first position at which the strings differ. Otherwise, the number returned is their common length.

Examples:

> (string<= "ab" "cd")

0

> (string<= "ab" "ab")

2

> (string<= 'symbol "string")

/Volumes/Maldis/Users/cce/plt/research/dracula/release/src/l

anguage/checking-proc.scm:36:21: Dracula program broke the

contract (-> string? string? any) on here; expected

<string?>, given: symbol

(string> x y) → t

x : (stringp x)

y : (stringp y)

Compares the two strings for lexicographical ordering. Returns non-nil if and only if y precedes x lexicographically. When non-nil, the number returned is the first position at which the strings differ.

Examples:

> (string> "ab" "cd")

()

> (string> "ab" "ab")

()

> (string> "ba" "ab")

0

> (string> 'symbol "string")

/Volumes/Maldis/Users/cce/plt/research/dracula/release/src/l

anguage/checking-proc.scm:36:21: Dracula program broke the

contract (-> string? string? any) on here; expected

<string?>, given: symbol

(string>= x y) → t

x : (stringp x)

y : (stringp y)

Compares the two strings for lexicographical ordering. Returns non-nil if and only if y precedes x lexicographically. If they differ, the number returned is the first position at which the strings differ. Otherwise, the number returned is their common length.

Examples:

> (string>= "ab" "cd")

()

> (string>= "ab" "ab")

2

> (string>= "ba" "ab")

0

> (string>= 'symbol "string")

/Volumes/Maldis/Users/cce/plt/research/dracula/release/src/l

anguage/checking-proc.scm:36:21: Dracula program broke the

contract (-> string? string? any) on here; expected

<string?>, given: symbol

(stringp x) → t

x : t

Determines whether x is a string.

Examples:

> (stringp "abcd")

t

> (stringp nil)

()