Actionscript allows us to use a parameterized **Vector** class for an array-type data structure, in addition to the **Array** class. Unlike an **Array**, a **Vector** can only hold one type of data item. This restriction allows a **Vector** to be accessed more efficiently than an **Array**. So, a **Vector** should be used whenever possible.

A **Vector** in Actionscript is similar to an STL **vector** in C++. Both are parameterized by a data type and can grow or shrink as items are added or removed. Both the Actionscript and C++ types have many different operations for manipulating the vector types. Both vectors also use the less-than and greater-than symbols to bracket the parameter type. However, the Actionscript **Vector** requires an additional period before the parameter, as shown in the examples below.

### One-Dimensional Vectors

**Function Notation**

- var aMyVector:Vector.<int> = Vector.<int>([1, 2, 3]);
- var aMyArray:Array = Array(new Sprite());

var aMyVector:Vector.<DisplayObject> = Vector.<DisplayObject>(aMyArray);

**Constructor Notation**

- var aMyVector:Vector.<int> = new Vector.<int>();

aMyVector.push(1, 2); - var aMyVector:Vector..<int> = new Vector.<int>(2);
- var aMyVector:Vector.<int> = new Vector.<int>(2, true);

aMyVector[0] = 1;

aMyVector[1] = 2;

### Multi-dimensional Vectors

Above, we have several examples of how to create a **Vector**. The first example uses the *Vector()* function to create a **Vector** of 3 ints with the values *1*, *2*, and *3*. The second example uses the *Vector()* function to create a **Vector** of the base type **DisplayObject** from an **Array** of the derived type **Sprite**.

Using constructors, we have three examples below those; the constructor takes two parameters: an **uint** and a **Boolean** to set the size and the whether the size is fixed, respectively. Without any parameters, the constructor uses the default parameters *0* and *false* to create a **Vector** of size zero that can be resized, as we show in the first constructor notation example. In the second constructor example, we create a **Vector** of **ints** with size *2*. Since we did not specify a second argument, the **Vector** does not have a fixed size. In the last example, we create a **Vector** of **ints** with size 2 that has a fixed size, since the second parameter is *true*. We use the bracket operator to fill the first and second entries with *1* and *2*, respectively.

- var aaMyVector:Vector.<Vector.<int>> = new Vector.<Vector.<int>>(3, true);

aaMyVector[0] = new Vector.<int>(2, true);

aaMyVector[1] = new Vector.<int>(2, true);

aaMyVector[2] = new Vector.<int>(2, true);aaMyVector[0][0] = 1;

aaMyVector[1][0] = 2;

aaMyVector[2][0] = 3;

aaMyVector[0][1] = 4;

aaMyVector[1][1] = 5;

aaMyVector[2][1] = 6;

Just as we did for **Arrays**, we can create multi-dimensional **Vectors** recursively. We can combine any of the methods for creating one-dimensional **Vectors** to do this. However, we limit ourselves to one example to avoid confusion. In this example, we create a **Vector** of 3 **int** **Vectors**. Next we create a new **Vector** of **ints** for each entry of this **Vector**. Finally, we use the double bracket operator to assign each entry a value.

Tags: 3.0, actionscript, adobe, declare, flash, programming, vector, web

By: Michael Hall

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