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How to return a 2-Dimensional array in C using a pointer

here's an example of a C function that performs matrix calculation and returns the result as a pointer to a separate function:

  


#include 
#include 

// Function to perform matrix multiplication
double* matrix_multiply(double* matrix1, double* matrix2, int rows1, int cols1, int cols2) {
    double* result = (double*)malloc(rows1 * cols2 * sizeof(double)); // Allocate memory for the result matrix
    int i, j, k;
    for (i = 0; i < rows1; i++) {
        for (j = 0; j < cols2; j++) {
            result[i*cols2+j] = 0; // Initialize the result element to 0
            for (k = 0; k < cols1; k++) {
                result[i*cols2+j] += matrix1[i*cols1+k] * matrix2[k*cols2+j]; // Perform matrix multiplication
            }
        }
    }
    return result; // Return the pointer to the result matrix
}

int main() {
    double matrix1[2][3] = {{1, 2, 3}, {4, 5, 6}}; // Define the first matrix
    double matrix2[3][2] = {{1, 2}, {3, 4}, {5, 6}}; // Define the second matrix
    int rows1 = 2, cols1 = 3, cols2 = 2; // Define the dimensions of the matrices

    // Call the matrix_multiply function and store the result in a pointer
    double* result = matrix_multiply(&matrix1[0][0], &matrix2[0][0], rows1, cols1, cols2);

    // Print the result matrix
    int i, j;
    for (i = 0; i < rows1; i++) {
        for (j = 0; j < cols2; j++) {
            printf("%.2f ", result[i*cols2+j]);
        }
        printf("\n");
    }

    free(result); // Free the memory allocated for the result matrix

    return 0;
}


  

In this example, the matrix_multiply function takes in two matrices (matrix1 and matrix2) and their dimensions (rows1, cols1, and cols2) as parameters. It allocates memory for the result matrix, performs the matrix multiplication, and returns the pointer to the result matrix. The main function defines two example matrices, calls matrix_multiply with these matrices and their dimensions, stores the pointer to the result matrix in a variable, and then prints the result matrix. Finally, it frees the memory allocated for the result matrix using the free function.

How to call a C function in Structure Text (Twincat ) ?

In the previous post I created a function returning a 2-D array in C . In this post propose some steps to call that function within a Twincat structure text program. To call a C function like struct Array2D matrixMultiplication(struct Array2D a, struct Array2D b) in TwinCAT Structured Text (ST), you can use the C-Callable Function Blocks (CCFBs) provided by TwinCAT. Here's an example of how to use a CCFB to call the matrixMultiplication function in ST:

  

PROGRAM MAIN
VAR
    a : ARRAY[1..3, 1..3] OF INT := [ [1, 2, 3], [4, 5, 6], [7, 8, 9] ];
    b : ARRAY[1..3, 1..3] OF INT := [ [9, 8, 7], [6, 5, 4], [3, 2, 1] ];
    c : ARRAY[1..3, 1..3] OF INT;
    a2d : STRUCT
        array : ARRAY[1..3, 1..3] OF INT;
    END_STRUCT;
    b2d : STRUCT
        array : ARRAY[1..3, 1..3] OF INT;
    END_STRUCT;
    c2d : STRUCT
        array : ARRAY[1..3, 1..3] OF INT;
    END_STRUCT;
    hLib : UINT := 0;
    pFunc : UINT := 0;
    result : INT := 0;
END_VAR

// Load the C library containing the matrixMultiplication function
hLib := SysLibLoad('MyLibrary.dll');

// Get the address of the matrixMultiplication function
pFunc := SysLibGetProcAddress(hLib, 'matrixMultiplication');

// Convert the input matrices to C-compatible data types
a2d.array := a;
b2d.array := b;

// Call the matrixMultiplication function using a CCFB
result := CCFBInvoke(pFunc, ADR(a2d), ADR(b2d), ADR(c2d));

// Check the result of the function call
IF result = 0 THEN
    // Convert the output matrix to ST-compatible data type
    c := c2d.array;
ELSE
    // Handle the error
END_IF

// Unload the C library
SysLibFree(hLib);


  

In this example, we define the input matrices a and b, and the output matrix c as ST arrays.

 We also define three STRUCT types a2d, b2d, and c2d, which have the same layout as the struct Array2D type used in the matrixMultiplication function.

Next, we load the C library containing the matrixMultiplication function using SysLibLoad, and get the address of the function using SysLibGetProcAddress. 

We then use the CCFBInvoke function to call the matrixMultiplication function, passing in the converted input matrices a2d and b2d, and the output c2d. 

 If the function call succeeds, the resulting c2d structure contains the output matrix, which we convert back to an ST array and store in c. If the function call fails, we can handle the error appropriately.

 Finally, we unload the C library using SysLibFree. 

 Note that you will need to compile the matrixMultiplication function into a DLL or shared library in order to load and call it from TwinCAT. 

 I will try to make a youtube video on this post as soon as possible.

How to return a 2-Dimensional array in C using a Structure

In C, it is not possible to return a 2-D array directly. However, we can return a struct that contains a 2-D array. Here's an example function that creates a 2-D array of integers and returns it as part of a struct:

  


#include 

struct Array2D {
  int array[3][3];
};

struct Array2D matrixMultiplication(struct Array2D a, struct Array2D b) {
    
  struct Array2D result  {0};
  int i, j, k;

  for (i = 0; i < 3; i++) {
    for (j = 0; j < 3; j++) {
      result.array[i][j] = 0;
      for (k = 0; k < 3; k++) {
        result.array[i][j] += a.array[i][k] * b.array[k][j];
      }
    }
  }

  return result;
}

int main() {
  struct Array2D a = {
    {{1, 2, 3},
     {4, 5, 6},
     {7, 8, 9}}
  };

  struct Array2D b = {
    {{9, 8, 7},
     {6, 5, 4},
     {3, 2, 1}}
  };

  struct Array2D c = matrixMultiplication(a, b);

  // Print the result
  printf("Result of matrix multiplication:\n");
  for (int i = 0; i < 3; i++) {
    for (int j = 0; j < 3; j++) {
      printf("%d ", c.array[i][j]);
    }
    printf("\n");
  }

  return 0;
}



  

We could also write similar function which return a pointer instead of structure See this post

What is React Child to Parent communicaiton ?

 In React with TypeScript, child-to-parent communication is typically achieved by passing callbacks from the parent component to its child components as props. The child component can then call the callback to send data or events back to the parent component.

Here's an example of how this might look in code:

In this example, the ChildComponent receives a onMessage callback function as a prop from its parent ParentComponent. When the user submits the form in the ChildComponent, the handleSubmit function is called and it calls the onMessage callback with the current value of the input field.

The ParentComponent handles the onMessage callback by setting the message state to the value passed by the child component. This causes the ParentComponent to re-render with the updated message value, which is then displayed on the screen.

This is a simple example, but it demonstrates the basic concept of passing callbacks from a parent component to its child components in React with TypeScript, and using those callbacks to send data or events back to the parent component.

What is React Parent to child communicaiton ?

 In React with TypeScript, parent-to-child communication is typically achieved by passing props from the parent component to its child components.

When a parent component renders a child component, it can pass data or functions to the child component using props. The child component can then access this data or functions through its props and use them as needed.

Here's an example of how this might look in code:

In this example, the ParentComponent passes two props to the ChildComponent: the count variable and the handleIncrement function. The ChildComponent then renders a button that calls the onIncrement function when clicked, and also displays the count prop.

This is a simple example, but it demonstrates the basic concept of passing data and functions from a parent component to its child components in React with TypeScript.

what is side effects and lifecycle in React ?

 In React with TypeScript, a "side effect" refers to any behavior that occurs outside the component's render cycle, such as modifying the DOM, making an API request, or updating a global state.

In functional components, side effects are managed using the useEffect hook. This hook allows you to perform an action when the component mounts, updates, or unmounts. Here's an example of using useEffect to fetch data from an API:

In this example, the useEffect hook is used to make an API request when the component mounts, and updates the data state with the response. The second argument to useEffect is an array of dependencies, which determines when the effect should run. An empty array means it only runs once, when the component mounts.

The "lifecycle" of a component refers to the different stages it goes through from creation to removal. In class components, these stages are defined by a set of lifecycle methods, such as componentDidMount, componentDidUpdate, and componentWillUnmount. In functional components, the useEffect hook is used to manage these stages.

The React component lifecycle can be represented by the following methods:

• componentDidMount: called once when the component is first mounted
• componentDidUpdate: called after the component updates (i.e. state or props change)
• componentWillUnmount: called when the component is about to be removed from the DOM

In functional components, you can use useEffect to perform similar tasks. The useEffect hook can be used to mimic the behavior of all three of the above methods:

• useEffect(() => { ... }, []) - mimics componentDidMount
• useEffect(() => { ... }) - mimics componentDidUpdate
• useEffect(() => { return () => { ... } }) - mimics componentWillUnmount

what is a Hook in React ?

In React TypeScript, a hook is a special function that allows functional components to use state and other React features that were previously only available in class components. Hooks allow you to reuse stateful logic across multiple components without having to use higher-order components or render props. They also help to keep the logic of a component separate from its presentation, making your code more modular and easier to maintain. Some commonly used hooks in React TypeScript include:

•   useState: allows you to add state to functional components 
•   useEffect: allows you to add side effects (e.g., data fetching, event listeners) to your components 
•  useContext: allows you to access a context object created by a ContextProvider component 
•  useRef: allows you to create a mutable reference that persists across renders 
•  useReducer: an alternative to useState that allows you to manage more complex state in a functional way .

To use a hook in a functional component, you simply call it at the top level of your component, and then use the values it returns in your JSX. For example:

In the example above, we're using the useState hook to add state to our Counter component. The hook returns an array with two values: the current state value (count) and a function to update the state (setCount). We then use these values to display the current count and update it when the button is clicked.

What is FC or function component in React ?

"FC" stands for "Functional Component". In React with TypeScript, a functional component is defined as a function that takes in props and returns JSX elements. The type of a functional component is typically defined using the FC type, which is short for FunctionComponent. For example, here's how you might define a functional component using FC in React with TypeScript:

In this example, MyComponent is a functional component that takes in name and age props of type string and number, respectively. The FC type definition at the top of the component definition tells TypeScript that this is a functional component that takes in props of type Props.

What is the use of CONST in React ?

In React and TypeScript, const is a keyword that is used to declare a variable that cannot be reassigned to a new value. Once a variable is declared with const, its value cannot be changed. Here's an example of using const to declare a variable in TypeScript:

  
 
const myNumber: number = 42;

  

In this example, we are declaring a variable myNumber with the value 42, and specifying that the type of the variable is number. Because const is used to declare the variable, we cannot reassign a new value to myNumber. In React, const is often used to declare variables that hold React components or functions. For example:

In this example, we are using const to declare a React function component called MyComponent. Inside the component, we are also declaring a function called myFunction using const. The onClick prop of the button element is then set to this function, so that when the button is clicked, the myFunction function is called and logs a message to the console. Overall, const is an important part of React and TypeScript syntax, as it allows you to declare variables that are immutable and cannot be changed once they are set. This can help make your code more reliable and easier to reason about.

What is Proptypes in React ?

PropTypes is a way of specifying the types of props that a React component expects to receive. PropTypes are a type checking feature that was originally introduced in React, but have since been moved to a separate prop-types package that can be used with React or other libraries. With PropTypes, you can define the expected types of your component's props and provide runtime validation to help catch errors and ensure that your component is used correctly. Here's an example of how to use PropTypes with a React functional component:

  
 
 import React from 'react';
import PropTypes from 'prop-types';

function Greeting(props) {
  return 
Hello, {props.name}!
;
}

Greeting.propTypes = {
  name: PropTypes.string.isRequired,
};

export default Greeting;


  

In this example, we define a functional component named Greeting that takes a single prop named name. We use the propTypes property to define the expected type of the name prop as a string, and we mark it as required using the isRequired method. This means that if the name prop is not provided, or is not a string, a warning will be printed in the console at runtime. This can help catch errors early and make it easier to debug your code. PropTypes are a powerful tool for ensuring that your React components are used correctly, but they are not strictly necessary. As an alternative, you can use TypeScript or other static type checkers to achieve similar type checking functionality.

The spread syntax or the rest syntax in Javascript or Typescript

In JavaScript and TypeScript, the ... syntax is called the spread syntax or the rest syntax, depending on the context in which it is used. When used in an array or an object, the spread syntax can be used to create a copy of the array or object and add or remove elements. Here's an example of using the spread syntax with an array:

  
 
const arr1 = [1, 2, 3];
const arr2 = [...arr1, 4, 5, 6];

console.log(arr2); // [1, 2, 3, 4, 5, 6]


  

In this example, we are creating a new array arr2 that is a copy of arr1 with the values 4, 5, and 6 added to the end. The spread syntax is used to "spread" the elements of arr1 into the new array, and then the additional elements are appended. Similarly, the spread syntax can be used with objects to create a new object with the properties of the original object, and add or overwrite properties. Here's an example:

  
 
const obj1 = { a: 1, b: 2 };
const obj2 = { ...obj1, b: 3, c: 4 };

console.log(obj2); // { a: 1, b: 3, c: 4 }



  

In this example, we are creating a new object obj2 that has all the properties of obj1, but with the value of b changed to 3 and a new property c added. The spread syntax is used to "spread" the properties of obj1 into the new object, and then the additional properties are added or overwritten. The spread syntax can also be used in function arguments to pass an array or an object as individual arguments. Here's an example:

  
 
const myFunc = (a: number, b: number, c: number) => {
  console.log(a + b + c);
};

const arr = [1, 2, 3];
myFunc(...arr); // 6

const obj = { a: 1, b: 2, c: 3 };
myFunc(...Object.values(obj)); // 6




  

In this example, we have a function myFunc that takes three arguments. We can use the spread syntax to pass the elements of an array or the values of an object as separate arguments to the function. In both cases, the function will receive the individual values 1, 2, and 3, and log the sum 6 to the console.

how to create a solr document with autogenerated unique id ?

how to create a solr document with autogenerated unique id ? You can create a Solr document with an auto-generated unique ID by not specifying the ID field (i.e., id) when adding the document to Solr. If you do not specify an ID, Solr will automatically generate a unique ID for the document.

  
import org.apache.solr.client.solrj.SolrClient;
import org.apache.solr.client.solrj.SolrServerException;
import org.apache.solr.client.solrj.impl.HttpSolrClient;
import org.apache.solr.common.SolrInputDocument;

import java.io.IOException;

public class SolrJExample {
    public static void main(String[] args) throws SolrServerException, IOException {
        String solrUrl = "http://localhost:8983/solr/your_core_name";
        SolrClient solrClient = new HttpSolrClient.Builder(solrUrl).build();

        SolrInputDocument document = new SolrInputDocument();
        document.addField("field1", "value1");
        document.addField("field2", "value2");

        solrClient.add(document);
        solrClient.commit();
    }
}