Assigning Values to an Array
You are encouraged to solve this task according to the task description, using any language you may know.
In this task, the goal is to assign a value to an element of an array. The value should only replace an existing value, and not insert a new key should the key not exist. If the key does not exist, an error should be returned.
ActionScript
arr[0] = 1; arr[1] = 'a'; arr[2] = 5.678;
Ada
package Pkg is
type Arr is array (Positive range <>) of Integer;
procedure Assign (Value : Integer; To : in out Arr; Index : Positive);
-- Raise exception Constraint_Error if Index > To'Last
end Pkg;
package body Pkg is
procedure Assign (Value : Integer; To : in out Arr; Index : Positive) is
begin
To (Index) := Value;
end Assign;
end Pkg;
(
ALGOL 68
Declarations:
FLEX [1:8] INT array:=(1,2,3,4,5,6,7,8); INT index=1, from=3, to=5, value=333;
Simple bound checking:
IF LWB array <= index AND UPB array >= index THEN
For a single index/value assignment:
array[index] := value;
To assign multiple values to multiple indices/slice:
array[from:to] := (33,44,55);
Replaces the 4th, 5th and 6th elements with the 33, 44 and 55.
To append/grow the end of the array:
PROC append int = (REF FLEX [] INT a, INT v)VOID: (
HEAP FLEX [LWB a:UPB a + 1] INT out;
out[:UPB a]:= a;
out[UPB out] := v;
a := out
);
append int(array,value);
print((array,new line))
FI
Result:
+333 +2 +33 +44 +55 +6 +7 +8 +333
AppleScript
set item location of array to value
To put an item on the end of a list:
set end of array to item
Brainf***
To assign values 5, 6, and 7 to array elements 1,2,3:
[-]>[-]>[-] zero array elements << go back to index 1 +++++ move value 5 to element 1 >++++++ move value 6 to element 2 >+++++++ move value 7 to element 3
C
int writeToIntArray(int *array, size_t array_sz, int loc, int val)
{
// Check bounds on array
if (loc > array_sz || loc < 0)
return -1;
array[loc] = val;
return 0;
}
C#
Language Version: 1.0+
public void WriteToIntArray(int[] array, int loc, int val){ array[loc]=val; }
C++
template<class T, std::size:t size>
inline int writeToArray(T (&array)[size], size_t loc, const T& val)
{
if (loc >= size)
return -1; // Could throw an exception if so desired
array[loc] = val;
return 0;
}
template<class C>
inline void writeToArray(C& container, typename C::size_type loc, const typename C::value_type& val)
{
std::fill_n(container.begin() + loc, 1, val);
}
ColdFusion
<cffunction name="writeToArray">
<cfargument name="array">
<cfargument name="location">
<cfargument name="value">
<cfif arrayLen(arguments.array) GTE arguments.location>
<cfset arguments.array[arguments.location] = arguments.value>
<cfelse>
<cfthrow message="Location does not exist">
</cfif>
<cfreturn arguments.array>
</cffunction>
<cfset myArray = arrayNew(1)>
<cfset myArray[1] = 1>
<cfset myArray = writeToArray(myArray, 1, 123456)>
Note that throwing errors in ColdFusion doesn't give that "friendly" appearance. The standard way to change/add a value in an array would be simply:
<cfset myArray[3] = 987654>
Common Lisp
(setf (aref array index) value)
D
void setValue(T) (T[] array, size_t index, T newValue) { array[index] = newValue; }
Delphi
procedure WriteToIntArray(var Arr: array of Integer; Loc: Integer; Val: Integer);
begin
Arr[Loc] := Val;
end;
Forth
Interpreter: ANS Forth
: ]! ( n addr ix -- ) cells + ! ; \ ex. 3 buffer[ 2 ]!
Fortran
Compiler: Any ANSI F77 (e.g. g77)
a(55) = 12
Haskell
List
Most Haskell programs use lists instead of arrays. This is suitable for the general case.
Simple Version
setIndex
:: [a] -- Original list
-> Int -- Index to insert at
-> a -- Value to insert
-> [a] -- Resulting list
setIndex xs ii v =
let
(h, (_ : ts)) = splitAt ii xs
in
h ++ (v : ts)
Efficient Version
setIndex xs ii v
| ii < 0 = error "Bad index"
| otherwise = _setIndex xs ii v
where
_setIndex [] _ _ = error "Bad index"
_setIndex (_ : xs) 0 v = v : xs
_setIndex (x : xs) ii v = x : (setIndex xs (ii - 1) v)
Array
Technically, this creates clones the original array, then updates the new array; the original array still exists. This applies a list of changes to the array.
import Data.Array -- Create the array of data a1 = array (0, 4) [(ii, ii * 2) | ii <- [0 .. 4]] -- Update 1 entry a2 = a1 // [(2, 12)] -- Update several entries a3 = a1 // [(ii, ii + 10) | ii <- [1 .. 3]]
J
array =: 5 5 5 5 5 5 5 99 (3}) array NB. Simple update 5 5 5 99 5 5 5 array =: 99 (3}) array NB. In place 88 99 88 (2 3 4}) array NB. Multiple update 5 5 88 99 88 5 5
Java
<java>public void writeToIntArray(int[] array, int loc, int val){
array[loc]=val;
}</java>
Things that Java people call "arrays" generally don't use the "key/value" vocabulary. In Java, there is an object called a Map with keys and values that works for this task. Maps are sorted by some aspect of the key in Java (hash, address, or natural order). The only thing we need to change is an error for a non-existent key. <java>import java.util.TreeMap; public void addToMap(TreeMap<Integer, Integer> map, int key, int val){
if(!map.containsKey(key)){
Systen.err.println("Key does not exist");
return;
}
map.put(key,val);
}</java>
JavaScript
function setElem(array, loc, val) { //returns 0 if out of bounds
if(typeof array[loc] == typeof undefined) {
return 0; //element doesn't already exist -- out of bounds
} else {
array[loc] = val
return 1; //OK
}//if
}//setElem
//use:
var ary=[10,20,30] //0,1,2 defined
var ok = setElem(ary,3,'three')
if(!ok) alert('oops, error')
Simpler if you don't mind adding an element if it does not already exist:
function writeToArray(array, loc, val) { array[loc] = val; }
LSE64
10 array :array 0 array 5 [] ! # store 0 at the sixth cell in the array
mIRC Scripting Language
alias write2array { echo -a $array_write(MyArray, 2, 3, Rosetta) }
Objective-C
- (void)addValue:(id)value toArray:(NSMutableArray *)array position:(unsigned)pos
{
[array insertObject:value atIndex:pos];
}
OCaml
let writeToArray arr loc val = arr.(loc) <- val;;
variant:
let writeToArray = Array.set
Perl
For a single index/value assignment:
$array[$index] = $value;
To assign multiple values to multiple indices:
@array[@indexes] = @values;
To assign an array slice:
@array[3..5] = @values; # will replace the 4th, 5th and 6th elements with the first 3 values in @values
PHP
<?php
function writeToArray(&$array, $index, $value)
{
$array[$index] = $value;
}
// Usage example
writeToArray($array, 1, 6 );
?>
Note that this is a "function" based example, and the relevant acting code is the following
$array[$index] = $value;
This does not conform to the (somewhat arbitrary) specific requirements of the task, in that it does not return an error if the key index) does not exist. To satisfy the task requirements:
<?php
function writeToArray(&$array, $index, $value)
{
if(array_key_exists($index, $array)) $array[$index] = $value;
else return false;
}
// Usage example
writeToArray($array, 1, 6 );
?>
PL/SQL
Interpreter: Oracle compiler
set serveroutput on
declare
type myarray is table of number index by binary_integer;
x myarray;
i pls_integer;
begin
-- populate array
for i in 1..5 loop
x(i) := i;
end loop;
i :=0;
-- print array
loop
i := i + 1;
begin
dbms_output.put_line(x(i));
exception
when no_data_found then exit;
end;
end loop;
end;
/
Pop11
value -> array(index);
Note that normal Pop11 array signal error when accessing non existing values (all values within index bounds exist).
Python
To change existing item, (raise IndexError if the index does not exists):
array[index] = value
To append to the end of the array:
array.append(value)
Ruby
# To specify a value for a known index # Usage: arr[index] = value arr = 1,2,3,4,5 arr[0] = 10
# To push a value onto an array. This accepts single or multiple arguments: arr.push( 1 ) arr.push( 1, 2, 3 )
# You can also use the << operator with one argument: arr << 1
Scala
val array = new Array[int](10) // create a 10 element array of integers array(3) = 44 array(22) = 11 // java.lang.ArrayIndexOutOfBoundsException: 22
import scala.collection.mutable.ArrayBuffer val array2 = new ArrayBuffer[int] array2 += 1 array2 += 2 array2 += 3 array2(1) // 2 (zero based indexing) array2(1) = 33 array2.toString // ArrayBuffer(1,33,3)
var l = List(1,2,3) l = 44 :: l // List(44,1,2,3) l(2) // 2
Scheme
(vector-set! arr loc val)
Tcl
proc setIfExist {theVariable value} {
upvar 1 $theVariable variable
if {[info exists theVariable]} {
set theVariable $value
} else {
error "$theVariable doesn't exist"
}
}
Note that setIfExist is general purpose and works on regular variables as well as arrays:
setIfExist foo(bar) 10 ;# error if foo(bar) doesn't exist setIfExist x 10 ;# error if x doesn't exist
Toka
100 cells is-array foo 1000 10 foo array.put ( Put value '1000' into array 'foo' at slot '10' ) 10 chars is-array bar char: A 1 foo array.putChar ( Put value 'A' (ASCII code) into character array 'bar' at slot '1' )
Visual Basic
Language Version: 5.0+
Private Function writeToArray(intArray() As Integer, arraySize As Integer, loc As Integer, value As Integer) As Integer
If loc > arraySize Then
writeToArray = -1
Else
intArray(loc) = value
writeToArray = 0
End If
End Function
VBScript
Simple Example
Define our Array
Dim myArray (5)
Use a For Next loop to set the array data.
For i = 0 To 4 myArray(i) = i Next
Use a For Next loop and MsgBox to display the array data.
MsgBox("Print array values")
For i = 0 To 4
msgbox("myArray element " & i & " = " & myArray(i))
Next
Variable Array Length
Example where we don't know the required array size at the start and where we need to increase the array size as we go
Define an array - but we don't know how big yet.
Dim myArray2 ()
OK, now we know how big an array we need.
ReDim myArray2(3)
Load the array
For i = 0 To 2 myArray2(i) = i Next
Print the array
MsgBox("We've set the new array size and set the data")
For i = 0 To 2
MsgBox "myArray2 element " & i & " = " & myArray2(i)
Next
Now we need to make the array bigger. Note the Preserve keyword so that the existing data in the array is not lost when we resize it.
ReDim Preserve myArray2(5)
Load the array
For i = 3 To 4 myArray2(i) = i Next
Print the array
MsgBox ("We've increased the array size and loaded more data")
For i = 0 To 4
MsgBox "myArray2 element " & i & " = " & myArray2(i)
Next