Dynamic Array: Usage of dynamic array when user to allocate its size for storage during run time.Dynamic array store a contiguous collection of data.

The array indexing should be always integer type.

To allocate the size of a dynamic array, we have to use a new[] operator.

Example:

int dyn_arr [];

initial

begin

dyn_arr = new[10]; //Allocated 10 elements

end

How to resize a dynamic array?

Example:

initial

begin

dyn_arr = new[25](dyn_arr); //Resize the Array and Copy

end

Dynamic Array Methods:

function int size()
- Returns the current size of the array
function void delete()
- Empties array contents and zero-sizes it

int my_addr[ ] = new[256];

initial begin

$display("Size of my_addr = %0d", my_addr.size() );

my_addr.delete();

$display("Size of my_addr (after delete) = %0d", my_addr.size());

end

Associative Array:

It is also allocated during run time.
This is the array, user need when data is sparse.
It is used when we don’t have to allocate contiguous collection of data, or data in a proper sequence or index.
Indexing is not regular, can be accessed using indexing like integer or string type or any scalar.

Example:

bit i_array[*]; // associative array of bits (unspecified index)

// unspecified index (*) implies any integral value

bit [7:0] age [string]; // associative array of 8-bit vectors, indexed by string

initial

begin

string tom = “tom”;

age [tom] = 21;

age [“joe”] = 32;

$display("%s is %d years of age ", tom, age[tom], "[%0d ages available]", age.num());

end

Associative Array Methods:

function int num()
- Returns the number of entries in the array, if empty returns 0
function void delete( [input index] )
- Index is optional
- If index is specified, deletes the item at the specified index
- If index is not specified the all elements in the array are removed
function int exists ( input index );
- Checks if an element exists at the specified index within the given array.
- Returns 1 if the element exists, otherwise it returns 0
function int first( ref index )
- Assigns to the given index variable the value of the first (smallest) index in the associative array
- It returns 0 if the array is empty, and 1 otherwise
function int last( ref index )
- Assigns to the given index variable the value of the last (largest) index in the associative array
- It returns 0 if the array is empty, and 1 otherwise.
function int next( ref index );
- finds the entry whose index is greater than the given index. If there is a next entry, the index variable is assigned the index of the next entry, and the function returns 1
- Otherwise, index is unchanged, and the function returns 0
function int prev( ref index );
- finds the entry whose index is smaller than the given index. If there is a previous entry, the index variable is assigned the index of the previous entry, and the function returns 1
- Otherwise, the index is unchanged, and the function returns 0

Queue:

Queue is a variable size, ordered collection of Homogenous Data.
It is flexible, as it is variable in size and analogous to an 1-dimensional Unpacked array that can shrink & grow automatically and can be of size zero.
The main advantage of queue over dynamic array is that, we don’t need new[] operator to allocate storage space for a queue.
The other advantages of queue over dynamic array is that we can manipulate the queue using various queue methods like: push, pop, delete, insert, size.

Example:

module test_example ;

int my_queue[$] = { 1, 2, 3 };

string s_queue [$] = {"first","second","third","fourth"};

string store;

initial

begin

// Use of the size() method/operator

$display("\n size() operator used");

for (int i = 0 ; i < my_queue.size(); i++ )

$display (my_queue[i]);

$display("\n\n Elements of s_queue is :");