## vector-lib

A library of vector operations for Chicken, based on the reference implementation in SRFI 43: Vector library.

This document contains the salient parts of the original SRFI 43 documentation. Chicken fully implements SRFI 43, with the following notes:

`list->vector`and`reverse-list->vector`take optional`start`and`end`arguments. Although not documented in the SRFI proper, the functionality is present in the reference implementation.- Procedures which are exactly equivalent to their R5RS counterparts have been omitted from this library:
`vector vector? make-vector vector-ref? vector-set! vector-length`.

## Procedures

In this section containing specifications of procedures, the following notation is used to specify parameters and return values:

`(f arg_1 arg_2 ···) -> something`- Indicates a function
`f`takes the parameters`arg_1 arg_2 ···`and returns a value of the type`something`. If`something`is`unspecified`, then what`f`returns is implementation-dependant; this SRFI does not specify what it returns, and in order to write portable code, the return value should be ignored. `vec`- The argument in this place must be a vector, i.e. it must satisfy the predicate
`vector?`. `i, j, start, size`- The argument in this place must be a nonnegative integer, i.e. it must satisfy the predicates
`integer?`and either`zero?`or`positive?`. The third case of it indicates the index at which traversal begins; the fourth case of it indicates the size of a vector. `end`- The argument in this place must be a positive integer, i.e. it must satisfy the predicates
`integer?`and`positive?`. This indicates the index directly before which traversal will stop — processing will occur until the the index of the vector is`end`. It is the closed right side of a range. `f`- The argument in this place must be a function of one or more arguments, returning exactly one value.
`pred?`- The argument in this place must be a function of one or more arguments that returns one value, which is treated as a boolean.
`x, y, z, seed, knil, fill, key, value`- The argument in this place may be any Scheme value.
`[something]`- Indicates that
`something`is an optional argument; it needn't necessarily be applied.`Something`needn't necessarily be one thing; for example, this usage of it is perfectly valid:`[start [end]]`and is indeed used quite often. `something ···`- Indicates that zero or more
`something`s are allowed to be arguments. `something_1 something_2 ···`- Indicates that at least one
`something`must be arguments. `something_1 something_2 ··· something_n`- Exactly equivalent to the previous argument notation, but this also indicates that
`n`will be used later in the procedure description.

It should be noted that all of the procedures that iterate across multiple vectors in parallel stop iterating and produce the final result when the end of the shortest vector is reached. The sole exception is `vector=`, which automatically returns `#f` if the vectors' lengths vary.

### Constructors

*[procedure]*

`(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 `k`th 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.

Examples:

(vector-unfold (λ (i x) (values x (- x 1))) 10 0) ;=> #(0 -1 -2 -3 -4 -5 -6 -7 -8 -8)

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))

*[procedure]*

`(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.

Examples:

Construct a vector in reverse of the integers in the range [0,`n`).

(vector-unfold-right (λ (i x) (values x (+ x 1))) n 0) ;=> #(n-1 n-2 ··· 2 1 0)

Reverse `vector`.

(vector-unfold-right (λ (i x) (values (vector-ref vector x) (+ x 1))) (vector-length vector) 0)

*[procedure]*

`(vector-copy vec [start [end [fill]]]) -> vector`

Allocates a new vector whose length is `end - start` and fills it with elements from `vec`, taking elements from `vec` starting at index `start` and stopping at index `end`. `start` defaults to `0` and `end` defaults to the value of `(vector-length vec)`. If `end` extends beyond the length of `vec`, the slots in the new vector that obviously cannot be filled by elements from `vec` are filled with `fill`, whose default value is unspecified.

Examples:

(vector-copy '#(a b c d e f g h i)) ;=> #(a b c d e f g h i)

(vector-copy '#(a b c d e f g h i) 6) ;=> #(g h i)

(vector-copy '#(a b c d e f g h i) 3 6) ;=> #(d e f)

(vector-copy '#(a b c d e f g h i) 6 12 'x) ;=> #(g h i x x x)

*[procedure]*

`(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)

*[procedure]*

`(vector-append vec ···) -> vector`

Returns a newly allocated vector that contains all elements in order from the subsequent locations in `vec ···`.

Examples:

(vector-append '#(x) '#(y)) ;=> #(x y)

(vector-append '#(a) '#(b c d)) ;=> #(a b c d)

(vector-append '#(a #(b)) '#(#(c))) ;=> #(a #(b) #(c))

*[procedure]*

`(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)

### Predicates

*[procedure]*

`(vector-empty? vec) -> boolean`

Returns `#t` if `vec` is empty, i.e. its length is `0`, and `#f` if not.

Examples:

(vector-empty? '#(a)) ;=> #f

(vector-empty? '#(())) ;=> #f

(vector-empty? '#(#())) ;=> #f

(vector-empty? '#()) ;=> #t

*[procedure]*

`(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 elements `E_a` and `E_b`, `(elt=? E_a E_b)` returns a true value. `Elt=?` is always applied to two arguments. Element comparison must be consistent with `eq`; that is, if `(eq? E_a E_b)` results in a true value, then `(elt=? E_a E_b)` must also result in a true value. This may be exploited to avoid unnecessary element comparisons. (The reference implementation does, but it does not consider the situation where `elt=?` is in fact itself `eq?` to avoid yet more unnecessary comparisons.)

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

### Iteration

*[procedure]*

`(vector-fold kons knil vec_1 vec_2 ···) -> value`

The fundamental vector iterator. `Kons` is iterated over each index in all of the vectors, stopping at the end of the shortest; `kons` is applied as ` (kons i state (vector-ref vec_1 i) (vector-ref vec_2 i) ···) ` where `state` is the current state value — the current state value begins with `knil`, and becomes whatever `kons` returned at the respective 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 (index len str) (max (string-length str) len)) 0 vector-of-strings)

Produce a list of the reversed elements of `vec`.

(vector-fold (λ (index tail elt) (cons elt tail)) '() vec)

Count the number of even numbers in `vec`.

(vector-fold (λ (index counter n) (if (even? n) (+ counter 1) counter)) 0 vec)

*[procedure]*

`(vector-fold-right kons knil vec_1 vec_2 ···) -> 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 (index tail elt) (cons elt tail)) '() '#(a b c d)) ;=> (a b c d)

*[procedure]*

`(vector-map f vec_1 vec_2 ···) -> vector`

Constructs a new vector of the shortest size of the vector arguments. Each element at index `i` of the new vector is mapped from the old vectors by `(f i (vector-ref vec_1 i) (vector-ref vec_2 i) ···)`. The dynamic order of application of `f` is unspecified.

Examples:

(vector-map (λ (i x) (* x x)) (vector-unfold (λ (i x) (values x (+ x 1))) 4 1)) ;=> #(1 4 9 16)

(vector-map (λ (i x y) (* x y)) (vector-unfold (λ (i x) (values x (+ x 1))) 5 1) (vector-unfold (λ (i x) (values x (- x 1))) 5 5)) ;=> #(5 8 9 8 5)

(let ((count 0)) (vector-map (λ (ignored-index ignored-elt) (set! count (+ count 1)) count) '#(a b))) ;=> #(1 2) OR #(2 1)

(vector-map (λ (i elt) (+ i elt)) '#(1 2 3 4)) ;=> #(1 3 5 7)

*[procedure]*

`(vector-map! f vec_1 vec_2 ···) -> unspecified`

Similar to `vector-map`, but rather than mapping the new elements into a new vector, the new mapped elements are destructively inserted into `vec_1`. Again, the dynamic order of application of `f` unspecified, so it is dangerous for `f` to apply either `vector-ref` or `vector-set!` to `vec_1` in `f`.

*[procedure]*

`(vector-for-each f vec_1 vec_2 ···) -> unspecified`

Simple vector iterator: applies `f` to each index in the range [0, `length`), where `length` is the length of the smallest vector argument passed, and the respective list of parallel elements from `vec_1 vec_2 ···` at that index. In contrast with `vector-map`, `f` is reliably applied to each subsequent elements, starting at index 0, in the vectors.

Example:

(vector-for-each (λ (i x) (display x) (newline)) '#("foo" "bar" "baz" "quux" "zot"))

Displays:

foo bar baz quux zot

*[procedure]*

`(vector-count pred? vec_1 vec_2 ···) -> 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 `i` and each parallel element in the vectors at that index, in order.

Examples:

(vector-count (λ (i elt) (even? elt)) '#(3 1 4 1 5 9 2 5 6)) ;=> 3

(vector-count (λ (i x y) (< x y)) '#(1 3 6 9) '#(2 4 6 8 10 12)) ;=> 2

### Searching

*[procedure]*

`(vector-index pred? vec_1 vec_2 ···) -> exact nonnegative integer or #f`

Finds & returns the index of the first elements in `vec_1 vec_2 ···` 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

*[procedure]*

`(vector-index-right pred? vec_1 vec_2 ···) -> 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.

*[procedure]*

`(vector-skip pred? vec_1 vec_2 ···) -> exact nonnegative integer or #f`

Finds & returns the index of the first elements in `vec_1 vec_2 ···` 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 (x_1 x_2 ···) (not (pred? x_1 x_1 ···))) vec_1 vec_2 ···)

Example:

(vector-skip number? '#(1 2 a b 3 4 c d)) ;=> 2

*[procedure]*

`(vector-skip-right pred? vec_1 vec_2 ···) -> 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 all of the vectors *must* have the same length. This is equivalent to:

(vector-index-right (λ (x_1 x_2 ···) (not (pred? x_1 x_1 ···))) vec_1 vec_2 ···)

*[procedure]*

`(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. `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:

(λ (char_1 char_2) (cond ((char<? char_1 char_2) -1) ((char=? char_1 char_2) 0) (else 1)))

*[procedure]*

`(vector-any pred? vec_1 vec_2 ···) -> value or #f`

Finds the first set of elements in parallel from `vec_1 vec_2 ···` 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.

*[procedure]*

`(vector-every pred? vec_1 vec_2 ···) -> value or #f`

If, for every index `i` between 0 and the length of the shortest vector argument, the set of elements `(vector-ref vec_1 i) (vector-ref vec_2 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.

### Mutators

*[procedure]*

`(vector-swap! vec i j) -> unspecified`

Swaps or exchanges the values of the locations in `vec` at `i` & `j`.

*[procedure]*

`(vector-fill! vec fill [start [end]]) -> unspecified`

[*R5RS*+] Assigns the value of every location in `vec` between `start`, which defaults to `0` and `end`, which defaults to the length of `vec`, to `fill`.

*[procedure]*

`(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.

*[procedure]*

`(vector-copy! target tstart source [sstart [send]]) -> unspecified`

Copies a block of elements from `source` to `target`, both of which must be vectors, starting in `target` at `tstart` and starting in `source` at `sstart`, ending when `send - sstart` elements have been copied. It is an error for `target` to have a length less than `tstart + (send - sstart)`. `Sstart` defaults to `0` and `send` defaults to the length of `source`.

*[procedure]*

`(vector-reverse-copy! target tstart source [sstart [send]]) -> unspecified`

Like `vector-copy!`, but this copies the elements in the reverse order. It is an error if `target` and `source` are identical vectors and the target & source ranges overlap; however, if `tstart = sstart`, `vector-reverse-copy!` behaves as ` (vector-reverse! target tstart send) ` would.

### Conversion

*[procedure]*

`(vector->list vec [start [end]]) -> proper-list`

[*R5RS*+] Creates a list containing the elements in `vec` between `start`, which defaults to `0`, and `end`, which defaults to the length of `vec`.

*[procedure]*

`(reverse-vector->list vec [start [end]]) -> proper-list`

Like `vector->list`, but the resulting list contains the elements in reverse between the the specified range.

*[procedure]*

`(list->vector proper-list [start [end]])`

[*R5RS*+] Produce a vector containing the elements in `proper-list`, which must be a proper list, between `start`, whose default is 0, and `end`, whose default is the length of `list`. It is suggested that if the length of `list` is known in advance, the `start` and `end` arguments be passed, so that `list->vector` need not call `length` itself.

*[procedure]*

`(reverse-list->vector proper-list [start [end]]) -> vector`

Like `list->vector`, but the resulting list contains the elements in reverse of `proper-list`.

## About this egg

### Author

Taylor Campbell. Chicken maintainer: Jim Ursetto. Test suite by Peter Danenberg.

### Version history

- 1.2
- Sync to reference implementation as of 2008-01-12
- 1.1
- Final implementation port (2005-05-24 + patches) by Jim Ursetto
- 1.0
- Draft implementation port by William S. Annis

### License

The reference implementation is subject to the following copyright.

Copyright (C) Taylor Campbell (2003). All rights reserved. Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions: The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software. THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

The Chicken extension is covered under the 3-clause BSD license.

Copyright (c) 2005-2011 Jim Ursetto. All rights reserved. Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met: - Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer. - Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution. - Neither the name of the author nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission. THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.