fisothemes / TwinCAT-Abstract-Data-Structures

Exploring Abstract Data Structures in Structured Text for use in PLCs

TwinCAT-Abstract-Data-Structures

Exploring Abstract Data Structures in Structured Text for use in PLCs

This project looks at the implementation of the following data structures in TwinCAT:

• Dynamic Arrays
• Linked Lists [Singly, Doubly, Circular]
• Queues [Dynamic Array, Linked List]
• Stacks [Dynamic Array, Linked List]

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Dynamic Array

Zero indexed array that can change its size at run-time. The array will automatically resize itself when inserting an element in a position out of its bounds. See the POU called P_Dynamic_Array for examples. Listed below are some, not all, functionalities for manupulating data in the dynamic array. Just run the program and write the appropriate boolean variables whilst logged in.

Declaration:

(* <name of array> : FB_Dynamic_Array(<Interger to Initialisation array with>) *)

//Initalise array with 10 elements type 
fbDyn_Array : FB_Dynamic_Array(10);

Insertion:

(* <name of array>.Insert(<element to insert>, <position to insert element>) *)

// Insert element of value 33 in the 10 position in array
fbDyn_Array.Insert(33,10); 

Accessing:

(* <name of array>.Access(<position of element>) *)

// Get in the 3rd element on the array
IF bAccess THEN nAccess := fbDyn_Array.Access(2); bAccess := 0; END_IF

Resizing:

(* <name of array>.Resize(<new size>) *)

// Changes number of elements in array to five
fbDyn_Array.Resize(5);

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Linked List

A zero indexed list of elements in unchained location in memory linked together. This list is dynamic so it can be resized at run-time. Unlike dynamic arrays, it only takes up as much space as needed. The examples below demostrates some of the functionalities available. See P_Singly_Linked_List POU for more examples.

Declaration:

(* <name of list> : FB_<Singly, Doubly, Circular>_Linked_List *)

//Initalise list
fbLinked_List : FB_Singly_Linked_List;

Insertions:

(* 
    <name of list>.Create(<element to insert>); // Insert element at the end of the list
    <name of list>.Push(<element to insert>);   // Insert element at the start of the list
    <name of list>.Insert(<element to insert>, <position to insert element>) // Insert element at a specified location 
*)

// Insert 3 elements into the list
fbLinked_List.Create(1);
fbLinked_List.Push(3);
fbLinked_List.Insert(2,1);

Deletions:

(* 
    <name of list>.Pop(); // Remove element at the start of the list
    <name of list>.Push(<position of element>); // Remove element at a specified location
 *)

// Remove the last and first element from the list
fbLinked_list.Remove(2);
fbLinked_List.Pop();