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## 7.Array Functions

S-Lang includes many intrinsic functions that operate on arrays. The additional functions described here are defined in `arrayfuns.sl`.

## 7.1rearrange

Synopsis

Rearrange the elements of a 1-d array or list.

Usage

`rearrange (A, indices)`

Description

This function performs an in-place rearrangment of the the elements of an array according to the specified permutation, represented by the `indices` argument. The `indices` array is assumed to contain unique integers in the range `[0,length(A)-1]`.

Notes

The function modifies the elements of the `indices` array while it performs the rearrangement. The values will get restored upon return from function.

The algorithm used was derived from the DPPERM function, which is part of the SLATEC package. See http://gams.nist.gov/cgi-bin/serve.cgi/Package/SLATEC.

`array_reverse, array_swap`

## 7.2reverse

Synopsis

Reverse the elements of a 1-d array

Usage

`Array_Type reverse (Array_Type A)`

Description

The `reverse` function reverses the elements of a 1-d array and returns the result.

`shift`

## 7.3shift

Synopsis

Shift the elements of a 1-d array

Usage

`Array_Type shift (Array_Type A, Int_Type n)`

Description

The `shift` function shifts the elements of an array by a specified amount and returns the result. If `n` is positive, the ith element of the array will be shifted to the position `i-n` of the array. Elements for which `i-n` is less than 0 will be moved to the end of the array.

Example

``` A = [1,2,3,4,5,6,7,8,9]; B = shift (A, 3); % ==> B = [4,5,6,7,8,9,1,2,3]; C = shift (A, -1); % ==> C = [9,1,2,3,4,5,6,7,8]; ```

Notes

It many ways `rotate` would be a better name for this function.

`reverse, transpose`