**Name:**

Part - returns a sub-array of an array

**Synopsis:**

array1 array2 Part -> array3

**Examples:**

[ [3 5 6 9] [11 4 7 2] [-9 1 8 10] ] [ [1 3] [2 3] ] Part --> [[5 6] [1 8]]

[ [3 [-12 -19] 6 9] [11 4 7 2] [-9 1 8 10] ] [ 1 2 2] Part --> -19

[3 4 5 6 7] [-2] Part --> 6

[3 [-9 -12] 5 6 7] [2] Part --> [-9 -12]

[3 [-9 -12] 5 6 7] [2 2] Part --> -12

[3 [-9 -12] 5 6 7] [[2 3]] Part --> [[-9 -12] 5]

[3 [-9 -12] 5 6 7] [[2 3 2]] Part --> [[-9 -12] 5 [-9 -12]]

[ [3 5 6 9] [11 4 7 2] [-9 1 8 10] ] [ 1 [] ] Part --> []

[ [3 5 6 9] [11 4 7 2] [-9 1 8 10] ] [ [] 1 ] Part --> []

[3 [5 -12] 6 9] [ [ 2 ] ] Part --> [[5 -12]]

[3 [5 -12] 6 9] [ [ 2 ] 2] Part --> [-12]

[ [3 5 6 9] [11 4 7 2] [-9 1 8 10] ] [ /All [3 2] ] Part --> [[6 5] [7 4] [8 1]]

**Description:**

Part returns a sub-array of array1 specified by

array2. This function is an implementation of

Mathematica's Part function. It can also be used

to rearrange or copy parts of array1. Note,

Mathematica-style functions in SLI use Mathematica

index notation.

**Parameters:**

array1 is an arbitrarily shaped array. In particular

it does not need to be rectangular.

array2 is an array [i,j, ...] where the i,j specify the

selected elements on each level. Any i,j can itself be

an array [i1,i2,....] specifying a list of elements on

that level. When i is the literal /All, all elements on

the corresponding level are returned. The first element

on each level has index 1. Indices can also be specified

counting from the end of the array, in this case the last

element has index -1. Positive and neative indices can

arbitrarily be intermixed.

Alternatives: Function Part_a (undocumented) -> behaviour and

synopsis are the same.

**Bugs:**

**Remarks:**

Literal /All plays the role of the index specifier ':'

in Matlab when used without arguments. Note, that

Matlab in addition provides specifier 'end'.

This is not necessary in the formalism of Mathematica

because indices counting from the end of the array can be

expressed by negative values.

**References:**

[1] The Mathematica Book V4.0 "Part"

**Author:**

Diesmann

**FirstVersion:**

29.9.1999

**SeeAlso:**

**Source:**

/home/nest/work/nest-2.14.0/lib/sli/mathematica.sli