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Array (Cross Ref > Data Structures)

Array

Languages Focus

A data structure in which individual values (called elements or items) may be located by reference to one or more integer index variables, the number of such indices being the number of dimensions in the array.

Arrays can start with an index value of 0 or 1, sometimes referred to as 0 based or 1 based.

Access VBA: x = Array()

Arrays in Access VBA use a 0-based indice. Use UBound to get the number of elements. UBound returns -1 if the array has no elements, 0 if it has 1, 1 if it has 2, etc.

Syntax Example:

Dim MyArray As Variant
Dim i As Integer
 
MyArray = Array("Mike", "Lisa", "Felicia", "Nathan")
 
If UBound(MyArray) > -1 Then
  For i = 0 To UBound(MyArray)
    MsgBox (MyArray(i))
  Next
End If

Linked Certification Question(s)

The following are practice certification questions with answers highlighted. These questions were prepared by Mike Prestwood and are intended to stress an important aspect of this KB post. All our practice questions are intended to prepare you generally for passing any certification test as well as prepare you for professional work.

Intermediate

1 Intermediate Level Question

Question #1: True or False?

Arrays in Access VBA are 0 based.

Answer:

True

False

More Info

To/From Code Guide: Array (Cross Ref > Data Structures) vs. Other Languages

ASP Classic: x = Array()

Arrays in ASP Classic use a 0-based indice.

Use UBound to get the number of elements. UBound returns -1 if the array has no elements, 0 if it has 1, 1 if it has 2, etc.

Syntax Example:

Dim MyArray, i

MyArray = Array("Mike", "Lisa", "Felicia", "Nathan")

If UBound(MyArray) > -1 Then
  For i = 0 to UBound(MyArray)

    Response.Write MyArray(i)

  Next

End If

Dynamically sized Arrays

Dim myArray()

Dim ArrayItem

ReDim Preserve myArray(0)     '&gt;&gt;&gt;0 based array.

myArray(0) = "Nathan"

ReDim Preserve myArray(1)

myArray(1) = "Felly"

''Loop thru array.
''''''''''''''''''
For Each ArrayItem In myArray

 Response.Write ArrayItem

Next

Looping

In addition to using a for each loop above, you can use a for loop as follows:

Dim myArray

Dim ArrayCounter

'...populate array here...

For ArrayCounter = 0 to UBound(myArray)
 Response.Write myArray(ArrayCounter)
Next

Linked Certification Question(s)

Intermediate

1 Intermediate Level Question

Question #1: Yes or No?

Are arrays in ASP Classic zero-based?

Answer:

Yes

More Info

To/From Code Guide: Array (Cross Ref > Data Structures) vs. Other Languages

Corel Paradox: Array[] type

Arrays in ObjectPAL use a 1-based subscript (also known as an index). Use [] with a subscript to refer to an element (i.e. MyArray[1], MyArray[2]).

The number of elements for a given array in ObjectPAL are either fixed or resizeable. Specify the size when you declare it for fixed. Use size() to get the number of elements, size() returns 0 if the array has no elements. Use setSize(), grow(), addLast(), etc. to add elements to an array.

Syntax Example:

var
  MyArray Array[4] String ;Fixed size array.
  i LongInt
endVar
MyArray[1] = "Mike"
MyArray[2] = "Lisa"
MyArray[3] = "Felicia"
MyArray[4] = "Nathan"
if MyArray.size() > 0 then
  for i from 1 to MyArray.size()
    msgInfo("", MyArray[i])
  endFor
endIf

ObjectPAL Array (Array[] type) 1 certification question.

The above example, is an example of a fixed size array in which you specified the size of the array when declared:

MyArray Array[4] String

Resizeable Arrays

With a resizeable array, you can set an initial size of the array and grow it as needed:

var

  MyArray Array[] String ;Resizeable array.

  i LongInt

endVar

MyArray.setSize(3)       ;Set initial size.

MyArray[1] = "Mike"

MyArray[2] = "Lisa"

MyArray[3] = "Felicia"

MyArray.setSize(4)      ;Reset size (truncates if you set smaller.)

MyArray[4] = "Nathan"

MyArray.Grow(1)         ;Add to the array with grow.

MyArray[5] = "Ingo"

if MyArray.size() &gt; 0 then

  for i from 1 to MyArray.size()

    msgInfo("", MyArray[i])

  endFor

endIf

Linked Certification Question(s)

Intermediate

1 Intermediate Level Question

Question #1: True or False?

An ObjectPAL array is 0-based, meaning, the first element has an index of 0.

Answer:

True

False

More Info

To/From Code Guide: Array (Cross Ref > Data Structures) vs. Other Languages

Code:

ObjectPAL Array (Array[] type)

Delphi: x=Array[0..3] of string;

Delphi supports both static and dynamic arrays as well as single and multi dimensional arrays.

Syntax Example:

var
  MyArray: array[0..3] of string;
  i: Integer;
begin
  MyArray[0] := 'Mike';
  MyArray[1] := 'Lisa';
  MyArray[2] := 'Felicia';
  MyArray[3] := 'Nathan';

  for i := 0 to High(MyArray) do
    ShowMessage(MyArray[i]);
end;

Delphi Array (x=Array[0..3] of string;) 1 certification question.

0-Based, 1-Based: A Choice

Because you can specify both he upper and lower index values when you declare a static array, you can specify 0 or 1 as the base index value. For example, you can rewrite the above code as:

var
  MyArray: array[1..4] of string;
  i: Integer;
begin
  MyArray[1] := 'Mike';
  MyArray[2] := 'Lisa';
  MyArray[3] := 'Felicia';
  MyArray[4] := 'Nathan';

  for i := Low(MyArray) to High(MyArray) do
    ShowMessage(MyArray[i]);
end;

Note the use of Low() in place of the base index value in the for loop.

In fact, you could specify any range you wish,

MyArray: array[6..9] of string;

or even:

MyArray: array[-1..2] of string;

You can also use an ordinal type such as Word or Byte directlry. For exaple, because a Byte is equivalent to 0..255 the following:

MyArray: array[Byte] of string;

is equivalent to:

MyArray: array[0..255] of string;

Initialize Global Arrays

You can initialize the values of a global array when you declare it, but not a local array. For example, the following code snippet is in the interface section of a unit.

var
  Form2: TForm2;
  MyArray2: array[0..1] of string = ('Mike', 'Lisa');

Linked Certification Question(s)

Beginner

1 Beginner Level Question

Question #1: Multiple Choice

Which is the correct syntax for declaring an array and setting two values of the array?

Answer:

Dim MyArray As Variant
MyArray = Array("Mike", "Lisa")

var
  MyArray Array[2] String
endVar

MyArray[1] = "Mike"
MyArray[2] = "Lisa"

var
  MyArray: array[0..3] of string;
begin
  MyArray[0] := 'Mike';
  MyArray[1] := 'Lisa';

end;

var
  MyArray: array[0..3] of string;
begin
  MyArray(0) = 'Mike';
  MyArray(1) = 'Lisa';

end;

var
  MyArray array(0..3) : string;
begin
  MyArray[0] := 'Mike';
  MyArray[1] := 'Lisa';

end;

More Info

To/From Code Guide: Array (Cross Ref > Data Structures) vs. Other Languages

VB Classic: x = Array()

Arrays in VB Classic use a 0-based indice. Use UBound to get the number of elements. UBound returns -1 if the array has no elements, 0 if it has 1, 1 if it has 2, etc.

Syntax Example:

Dim MyArray As Variant
Dim i As Integer
 
MyArray = Array("Mike", "Lisa", "Felicia", "Nathan")
 
If UBound(MyArray) > -1 Then
  For i = 0 To UBound(MyArray)
    MsgBox (MyArray(i))
  Next
End If

Linked Certification Question(s)

Intermediate

1 Intermediate Level Question

Question #1: True or False?

A VB classic array is 0-based, meaning the first index is 0.

Answer:

True

False

More Info

To/From Code Guide: Array (Cross Ref > Data Structures) vs. Other Languages