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► KB ► To/From Guides ► ASP Classic ► Data Structures

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Cross Ref > Data Structures

By Mike Prestwood

ASP Classic versus Delphi Prism: A side by side comparison between ASP Classic and Delphi Prism.

Data Structures

Data structures allow you to store and work with data. Common data structures include arrays, associative arrays, etc.

Array

[Other Languages]

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.

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: 1 certification question.

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

[Not specified yet. Coming...]

Associative Array

[Other Languages]

A set of unique keys linked to a set of values. Each unique key is associated with a value. Think of it as a two column table. MyArray['CA'] = 'California' MyArray['AR'] = 'Arizona'

Languages Focus

Associative arrays are also known as a dictionary or a hash table in other languages.

ASP Classic: Scripting.Dictionary

Use the scriptiing dictionary object which is available on later versions of ASP Classic (all still commonly in use).

Note: Both Access VBA and VB Classic use a collection for this but collections are not supported in ASP Classic.

Syntax Example:

Dim StateList

set StateList = Server.CreateObject("Scripting.Dictionary")
StateList.Add "CA", "California"
StateList.Add "NV", "Nevada"

Response.Write "I live in " & StateList.Item("CA")

ASP Classic Associative Array (Scripting.Dictionary)

[Not specified yet. Coming...]

Pointers

[Other Languages]

General Info: Pointers / References

A pointer is a variable type that allows you to refer indirectly to another object. Instead of holding data, a pointer holds the address to data -- the address of another variable or object. You can change the address value a pointer points to thus changing the variable or object the pointer is pointing to.

A reference is a type of pointer that cannot change and it must always point to a valid storage (no nulls).

ASP Classic: Not Supported

ASP Classic does not offer developer defined pointers.

Delphi Prism:

Although pointer data types in Prism coding are less important than in other languages such as C++, Prism does support developer defined pointers. Use the ^ operator to declare a pointer data type. Use the @ operator to return the current address of a variable.

In .Net managed coding the use of pointers is not safe because the garbage collector may move memory around. To safely use pointers, use the unsafe keyword. However, avoid unsafe code if possible.

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