SRFI 133 - Vector Library
The (srfi 133) provides a vector library.
See the SRFI document for more information.
Constructors
vector-unfold
vector-unfold-right
vector-reverse-copy
vector-concatenate
vector-append-subvectors
Predicates
Iteration
vector-fold
vector-fold-right
vector-map!
vector-count
vector-cumulate
Searching
vector-index
vector-index-right
vector-skip
vector-skip-right
vector-binary-search
vector-any
vector-every
vector-partition
Mutators
vector-swap!
vector-reverse!
vector-reverse-copy!
vector-unfold!
vector-unfold-right!
Conversion
reverse-vector->list
reverse-list->vector
vector-unfold
(vector-unfold f length initial-seed ...) -> vector
The fundamental vector constructor. Creates a vector whose length is length and iterates across each index k between 0 and length, applying f at each iteration to the current index and current seeds, in that order, to receive n + 1 values: first, the element to put in the kth slot of the new vector and n new seeds for the next iteration. It is an error for the number of seeds to vary between iterations. Note that the termination condition is different from the unfold procedure of SRFI 1.
Examples:
(vector-unfold (λ (i x) (values x (- x 1)))
10 0)
#(0 -1 -2 -3 -4 -5 -6 -7 -8 -9)
Construct a vector of the sequence of integers in the range [0,n).
(vector-unfold values n)
#(0 1 2 ... n-2 n-1)
Copy vector.
(vector-unfold (λ (i) (vector-ref vector i))
(vector-length vector))
vector-unfold-right
(vector-unfold-right f length initial-seed ...) -> vector
Like vector-unfold, but it uses f to generate elements from right-to-left, rather than left-to-right. The first index used is length - 1. Note that the termination condition is different from the unfold-right procedure of SRFI 1.
Examples:
Construct a vector of pairs of non-negative integers whose values sum to 4.
(vector-unfold-right (λ (i x) (values (cons i x) (+ x 1))) 5 0)
#((0 . 4) (1 . 3) (2 . 2) (3 . 1) (4 . 0))
Reverse vector.
(vector-unfold-right (λ (i x) (values (vector-ref vector x) (+ x 1)))
(vector-length vector)
0)
vector-reverse-copy
(vector-reverse-copy vec [start [end]]) -> vector
Like vector-copy, but it copies the elements in the reverse order from vec.
Example:
(vector-reverse-copy '#(5 4 3 2 1 0) 1 5)
#(1 2 3 4)
vector-concatenate
(vector-concatenate list-of-vectors) -> vector
Appends each vector in list-of-vectors. This is equivalent to:
(apply vector-append list-of-vectors)
However, it may be implemented better.
Example:
(vector-concatenate '(#(a b) #(c d)))
#(a b c d)
vector-append-subvectors
(vector-append-subvectors [vec start end] ...) -> vector
Returns a vector that contains every element of each vec from start to end in the specified order. This procedure is a generalization of vector-append.
Example:
(vector-append-subvectors '#(a b c d e) 0 2 '#(f g h i j) 2 4)
#(a b h i)
vector-empty?
(vector-empty? vec) -> boolean
Returns #t if vec is empty, i.e. its length is 0, and #f if not.
vector=
(vector= elt=? vec ...) -> boolean
Vector structure comparator, generalized across user-specified element comparators. Vectors a and b are considered equal by vector= iff their lengths are the same, and for each respective element Ea and Eb, (elt=? Ea Eb) returns a true value. Elt=? is always applied to two arguments.
If there are only zero or one vector arguments, #t is automatically returned. The dynamic order in which comparisons of elements and of vectors are performed is left completely unspecified; do not rely on a particular order.
Examples:
(vector= eq? '#(a b c d) '#(a b c d))
#t
(vector= eq? '#(a b c d) '#(a b d c))
#f
(vector= = '#(1 2 3 4 5) '#(1 2 3 4))
#f
(vector= = '#(1 2 3 4) '#(1 2 3 4))
#t
The two trivial cases.
(vector= eq?)
#t
(vector= eq? '#(a))
#t
Note the fact that we don’t use vector literals in the next two. It is unspecified whether or not literal vectors with the same external representation are eq?.
(vector= eq? (vector (vector 'a)) (vector (vector 'a)))
#f
(vector= equal? (vector (vector 'a)) (vector (vector 'a)))
#t
vector-fold
(vector-fold kons knil vec1 vec2 ...) -> value
The fundamental vector iterator. Kons is iterated over each value in all of the vectors, stopping at the end of the shortest; kons is applied as (kons state (vector-ref vec1 i) (vector-ref vec2 i) ...) where state is the current state value. The current state value begins with knil, and becomes whatever kons returned on the previous iteration, and i is the current index.
The iteration is strictly left-to-right.
Examples:
Find the longest string’s length in vector-of-strings.
(vector-fold (λ (len str) (max (string-length str) len))
0 vector-of-strings)
Produce a list of the reversed elements of vec.
(vector-fold (λ (tail elt) (cons elt tail))
'() vec)
Count the number of even numbers in vec.
(vector-fold (λ (counter n)
(if (even? n) (+ counter 1) counter))
0 vec)
vector-fold-right
(vector-fold-right kons knil vec1 vec2 ...) -> value
Similar to vector-fold, but it iterates right to left instead of left to right.
Example:
Convert a vector to a list.
(vector-fold-right (λ (tail elt) (cons elt tail))
'() '#(a b c d))
(a b c d)
vector-map!
(vector-map! f vec1 vec2 ...) -> unspecified
Similar to vector-map, but rather than mapping the new elements into a new vector, the new mapped elements are destructively inserted into vec1. Again, the dynamic order of application of f is unspecified, so it is dangerous for f to apply either vector-ref or vector-set! to vec1 in f.
vector-count
(vector-count pred? vec1 vec2 ...) -> exact nonnegative integer
Counts the number of parallel elements in the vectors that satisfy pred?, which is applied, for each index i in the range [0, length) where length is the length of the smallest vector argument, to each parallel element in the vectors, in order.
Examples:
(vector-count even? '#(3 1 4 1 5 9 2 5 6))
3
(vector-count < '#(1 3 6 9) '#(2 4 6 8 10 12))
2
vector-cumulate
(vector-cumulate f knil vec) -> vector
Returns a newly allocated vector new with the same length as vec. Each element i of new is set to the result of invoking f on newi-1 and veci, except that for the first call on f, the first argument is knil. The new vector is returned.
Example:
(vector-cumulate + 0 '#(3 1 4 1 5 9 2 5 6))
#(3 4 8 9 14 23 25 30 36)
vector-index
(vector-index pred? vec1 vec2 ...) -> exact nonnegative integer or #f
Finds & returns the index of the first elements in vec1 vec2 ... that satisfy pred?. If no matching element is found by the end of the shortest vector, #f is returned.
Examples:
(vector-index even? '#(3 1 4 1 5 9))
2
(vector-index < '#(3 1 4 1 5 9 2 5 6) '#(2 7 1 8 2))
1
(vector-index = '#(3 1 4 1 5 9 2 5 6) '#(2 7 1 8 2))
#f
vector-index-right
(vector-index-right pred? vec1 vec2 ...) -> exact nonnegative integer or #f
Like vector-index, but it searches right-to-left, rather than left-to-right, and all of the vectors must have the same length.
vector-skip
(vector-skip pred? vec1 vec2 ...) -> exact nonnegative integer or #f
Finds & returns the index of the first elements in vec1 vec2 ... that do not satisfy pred?. If all the values in the vectors satisfy pred? until the end of the shortest vector, this returns #f. This is equivalent to:
(vector-index (λ (x1 x2 ...) (not (pred? x1 x1 ...)))
vec1 vec2 ...)
Example:
(vector-skip number? '#(1 2 a b 3 4 c d))
2
vector-skip-right
(vector-skip-right pred? vec1 vec2 ...) -> exact nonnegative integer or #f
Like vector-skip, but it searches for a non-matching element right-to-left, rather than left-to-right, and it is an error if all of the vectors do not have the same length. This is equivalent to:
(vector-index-right (λ (x1 x2 ...) (not (pred? x1 x1 ...)))
vec1 vec2 ...)
vector-binary-search
(vector-binary-search vec value cmp) -> exact nonnegative integer or #f
Similar to vector-index and vector-index-right, but instead of searching left to right or right to left, this performs a binary search. If there is more than one element of vec that matches value in the sense of cmp, vector-binary-search may return the index of any of them.
cmp should be a procedure of two arguments and return a negative integer, which indicates that its first argument is less than its second, zero, which indicates that they are equal, or a positive integer, which indicates that the first argument is greater than the second argument. An example cmp might be:
(lambdaλ (char1 char2)
(cond ((char<? char1 char2) -1)
((char=? char1 char2) 0)
(else 1)))
vector-any
(vector-any pred? vec1 vec2 ...) -> value or #f
Finds the first set of elements in parallel from vec1 vec2 ... for which pred? returns a true value. If such a parallel set of elements exists, vector-any returns the value that pred? returned for that set of elements. The iteration is strictly left-to-right.
vector-every
(vector-every pred? vec1 vec2 ...) -> value or #f
If, for every index i between 0 and the length of the shortest vector argument, the set of elements (vector-ref vec1 i) (vector-ref vec2 i) ... satisfies pred?, vector-every returns the value that pred? returned for the last set of elements, at the last index of the shortest vector. The iteration is strictly left-to-right.
vector-partition
(vector-partition pred? vec) -> vector and integer
A vector the same size as vec is newly allocated and filled with all the elements of vec that satisfy pred? in their original order followed by all the elements that do not satisfy pred?, also in their original order.
Two values are returned, the newly allocated vector and the index of the leftmost element that does not satisfy pred?.
vector-swap!
(vector-swap! vec i j) -> unspecified
Swaps or exchanges the values of the locations in vec at i & j.
vector-reverse!
(vector-reverse! vec [start [end]]) -> unspecified
Destructively reverses the contents of the sequence of locations in vec between start and end. Start defaults to 0 and end defaults to the length of vec. Note that this does not deeply reverse.
vector-reverse-copy!
(vector-reverse-copy! to at from [start [end]]) -> unspecified
Like vector-copy!, but the elements appear in to in reverse order.
vector-unfold!
(vector-unfold! f vec start end initial-seed ...) -> unspecified
Like vector-unfold, but the elements are copied into the vector vec starting at element start rather than into a newly allocated vector. Terminates when end-start elements have been generated.
vector-unfold-right!
(vector-unfold-right! f vec start end initial-seed ...) -> unspecified
Like vector-unfold!, but the elements are copied in reverse order into the vector vec starting at the index preceding end`.
reverse-vector->list
(reverse-vector->list vec [start [end]]) -> proper-list
Like vector->list, but the resulting list contains the elements in reverse of vec.
reverse-list->vector
(reverse-list->vector proper-list) -> vector
Like list->vector, but the resulting vector contains the elements in reverse of proper-list.