Retrieving an Element of an Array

In this task, the goal is to retrieve an element of an array.

4D

  ` first element
$elem:=$array{1}

X86 assembly

Assembler: nasm

mov esi, array_offset
mov ebx, 2
mov eax, [esi+ebx*4]

ActionScript

var arr:Array = new Array(1,2,3);
var myVar:Number = arr[1];
// the value of myVar is: 2

AppleScript

on getArrayValue(array, location)
    -- very important -- The list index starts at 1 not 0
    return item location in array
end getArrayValue

C

 int array_index(int array[], int index) {
   return array[index];
 }

C#

 int getArrayValue( int values[], int index ) {
   return values[index];
 }

C++

 template<typename T>
 T array_index(T array[], size_t index) {
   return array[index];
 }

ColdFusion

<cfset arr = ArrayNew(1)>
<cfset arr[1] = "one">
<cfset arr[2] = "2">
<cfset arr[3] = 3>
<cfset var = arr[1]>

The value of var is "one"

ColdFusion Arrays are NOT zero-based, their index begins at 1

Common Lisp

  (defun array-value (array index)
    (aref array index))

Delphi/Object Pascal/Turbo Pascal/Standard Pascal

Array's in all the flavors of pascal can be of any valid base type, or user defined type ( which are all made up of base types ) and are multi-dimensional. With Delphi dynamic arrays were defined but had been used in pascal since its inseption.

A Static array defintion:

foo : array[1..10] of integer; { The base index is ONE }

The base index can be freely chosen:

foo: array[7 .. 16] of integer; { The base index is 7 }

Indeed, the "1 .. 10" resp. "7 .. 16" are actually types: they are integer subrange types. Arrays can also be indexed by enumeration types or enumeration subrange types:

type
 rainbowcolor = (red, orange, yellow, green, blue, violet);
var
 foo: array[rainbowcolor] of integer;
 bar: array[yellow .. blue] of integer;
 i: integer
begin
 i := foo[red]; { allowed indices are red, orange, yellow, green, blue, violet }
 i := bar[green]; { allowed indices are yellow, green, blue }
end;

A Dynamic Array type in Delphi:

foo : array of integer ; // The base index is ZERO

An "old school" dynamic array in the various flavors of pascal

foo : array[0..0] of integer;  // The base index is ZERO

A dynamic array in Extended Pascal:

type
 intarray(n: integer) = array[1 .. n] of integer; { base index 1 }
var
 foo: ^intarray;
begin
 new(foo, 10); { foo now has index 1 to 10 }
 i := foo[2];
 dispose(foo); { get rid of the array }
end;

In the case of the static array, the compiler generates the code to allocate the required memory to hold 10 integers.

In the Delphi style ---dynamic--- array you must set its length:

SetLength(foo,10);  // this array will no hold 10 integers

In the "old school" style of dynamic arrays, you created a point to the zero length declaration and then allocated memory to it with GetMem

pFoo : ^Foo ;
Foo  : array[0..0] of integer ;

All arrays are accessed the same way regardless of declaration method.

i : integer ;

i := foo[n] ;

where n is the array index who's base is either 1 or 0 depending on how it was declared.

Erlang

Erlang lists are 1-based which means that the index must be within the bounds (1 .. length(List)):

Value = lists:nth(Index, List).

Note that lists are implemented as linked-lists, hence this is operation is O(N).

Forth

Forth does not have special syntax for array access. Address arithmetic is used to access contiguous memory.

create array 1 , 2 , 3 , 4 ,
array 2 cells + @ .    \ 3

Groovy

Define an array

arr = ['groovy', 'is', 'a', 'great', 'language']

First element

arr[0] // *** 'groovy'

Last element, negative indexes

arr[-1] // *** 'language'

Ranges

arr[-3..-1] // *** ['a', 'great', 'language']

Mix n Match

arr[0..2, -1] // *** ['groovy', 'is', 'a', 'language']

Haskell

Arrays can have arbitrary bounds (not restricted to integer values, any instance of Ix will do):

import Data.Array

example = listArray (2,5) ["This", "is", "an", example"]

result = example ! 4

Here, result will be equal to "an". It should be noted that in Haskell lists are often used instead of arrays.

IDL

 ; this is allowed:
 result = arr(5) 
 ; but this is preferred:
 result = arr[5]

The form with square brackets is preferred as it unambiguously constitutes array access, while the version with round ones can conflict with a function call if there are both a function and an array with the same name arr.

Java

Object[] element = array[index];

JavaScript

var element = array[index];

LSE64

10 array :array
array 5 [] @     # contents of sixth cell in array

MAXScript

item = arr[index]

mIRC Scripting Language

Interpeter: mIRC Script Editor

Library: mArray Snippet

 alias readmyarray { echo -a $array_read(MyArray, 2, 3) }

Perl

Interpreter: Perl 5.8.8

$elem = $array[0];

PHP

$array = array('php', 'has', 'arrays');
// First element 
$elem  = $array[0];

Pop11

lvars ar = {1 two 'three'};
lvars elem;
;;; Access second element and assign to variable elem
ar(2) -> elem;

This example uses the simplest possible array (a vector). Pop11 has more general arrays, but in all cases access follows the same pattern, and look the same as procedure (function) call.

Python

Interpreter: Python 2.5

The item is an element in a list at a given index

 item = aList[index]

or

To use a list like a stack be it FIFO/LIFO

 aList.pop()  # Pop last item in a list
 aList.pop(0) # Pop first item in a list

Note: When using the pop() method, the element is removed from the list.

Ruby

 ary = ['Ruby','rules','big','time']
 #the first element
 element = ary[0]
 #or
 element = ary.first
 # => element = 'Ruby'

 #the last element
 element = ary[-1]
 #or
 element = ary.last
 # => element = 'time'

 #retrieving different values at once
 elements = ary.values_at(0,2,3)
 # => elements = ['Ruby','big','time']

 #select the first element of length 3
 element = ary.find{|el|el.length==3}
 # => element = "big"

Smalltalk

  #($a $b $c) at: 2

Tcl

All arrays in Tcl are associative. If "key" is the variable that holds the key of the element to be retrieved, then

 set result $array($key)

Toka

This retrieves the value 20 from the second item in the array:

 3 cells is-array table

 ( Populate the array )
 10 0 table array.put
 20 1 table array.put
 30 2 table array.put
 
 table 1 array.get