2.4.12 Sequences

(coerce x y) → t

x : (if (equal y 'list) (stringp x) (if (equal y 'string) (character-listp x) nil))

y : t

Coerces a character list into a string or a string into a list. The second argument must be either 'string or 'list.

Examples:

> (coerce "hello" 'list)

(#\h #\e #\l #\l #\o)

> (coerce '(#\h #\e #\l #\l #\o) 'string)

"hello"

> (coerce "hello" 'blah)

/Users/cce/plt/research/dracula/release/src/language/checkin

g-proc.scm:36:21: Dracula program broke the contract

(->r ((x ...) (result-type ...)) ...) on here; expected

<(symbols (quote list) (quote string))>, given: blah

(concatenate sym seq ...)

Concatenates strings or lists together. If the first argument is 'string, concatenate will accept strings to concatenate. If the first argument is 'list, it will accept lists.

Examples:

> (concatenate 'string "ab" "cd" "ef")

"abcdef"

> (concatenate 'string "ab")

"ab"

> (concatenate 'string)

""

> (concatenate 'list '(a b) '(c d) '(e f))

(a b c d e f)

> (concatenate 'list)

()

(length x) → t

x : (or (true-listp x) (stringp x))

Returns the number of elements in the given list, or the number of characters in the given string.

Examples:

> (length (list 1 2 3 4 5))

5

> (length "hello")

5

(position x seq) → t

x : t

seq : (or (stringp seq) (and (true-listp seq) (or (eqlablep x) (eqlable-listp seq))))

Determines the (0-based) position in seq at which x first occurs. Uses eql for comparisons. Returns nil if x is not found.

Examples:

> (position 1 (list 3 2 1))

2

> (position #\o "lion")

2

> (position 5 (list 1 2 3))

()

> (position "5" (list "1" "3" "5"))

/Users/cce/plt/research/dracula/release/src/language/checkin

g-proc.scm:36:21: Dracula program broke the contract (->r

((x ...) (y ...)) ...) on here; expected <eqlablep>, given:

"1"

(position-eq x lst) → t

x : t

lst : (and (true-listp lst) (or (symbolp x) (symbol-listp lst)))

Determines the (0-based) position in lst at which x first occurs. Uses eq for comparisons. Returns nil if x is not found.

Examples:

> (position-eq 'a (list 'c 'b 'a))

2

> (position-eq 5 (list 1 2 3 4 5))

/Users/cce/plt/research/dracula/release/src/language/checkin

g-proc.scm:36:21: Dracula program broke the contract (->r

((x ...) (y ...)) ...) on here; expected <symbolp>, given: 1

(position-equal x seq) → t

x : t

seq : (or (stringp seq) (true-listp seq))

Determines the (0-based) position in seq at which x first occurs. Uses equal for comparisons. Returns nil if x is not found.

Examples:

> (position-equal 'a (list 'c 'b 'a))

2

> (position-equal #\o "lion")

2

> (position-equal "5" (list "1" "3" "5"))

2

> (position-equal 5 12345)

/Users/cce/plt/research/dracula/release/src/language/checkin

g-proc.scm:36:21: Dracula program broke the contract (->

(or/c "nil" (cons/c any/c any/c)) any) on here; expected

<(or/c nil (cons/c any/c any/c))>, given: 12345

(subseq seq i j) → t

seq : (or (true-listp seq) (stringp seq))

i : ((integerp i) (<= 0 i))

j : (and (or (null j) (and (integerp j) (<= j (length seq)))) (<= i (or j (length seq))))

Returns a subsection of the given sequence, starting at the ith (inclusive, 0-based) position and ending at the jth (exclusive) position. If j is nil, then subseq will return the list to the end.

Examples:

> (subseq "0123456789" 2 6)

"2345"

> (subseq (list 0 1 2 3 4 5) 2 4)

(2 3)

> (subseq (list 0 1 2 3 4 5) 2 nil)

-: expects type <number> as 1st argument, given: (); other

arguments were: 2

> (subseq "abcdefgh" 4 1)

substring: ending index 1 out of range [4, 8] for string:

"abcdefgh"

(substitute new old seq) → t

new : t

old : t

seq : (or (and (stringp seq) (characterp new)) (and (true-listp seq) (or (eqlablep old) (eqlable-listp seq))))

Substitutes every occurrence of old with new in the given list or string.

Examples:

> (substitute 2 1 (list 1 1 1 3 1 1 1))

(2 2 2 3 2 2 2)

> (substitute #\Z #\a "abcdabcdabcd")

"ZbcdZbcdZbcd"