# Overview

D programming language is compatible with C++, which helps us link both programming languages using `extern(C++)`. After using this command, we can use the global function declared within the C++ file.

To use the global function, we first compile the C++ file separately. We can then call that function in our D program using the compiled C++ file.

Let's explore the syntax.

## Syntax

To call the C++ function from D, we use `extern(C++)`. Then, we add the function we want to use in the C++ file.

## Example

//declare the c++ function in d
extern (C++) int sum(int a, int b);

void main()
{
//calling the funtion and passing value in the parameter
    sum(4, 22);
}

#include <iostream>

using namespace std;
// Defining a c++ global fun
int sum(int a, int b)
{    
    cout << "Sum = " << a+b << endl;
   
    return 0;
}

import React from 'react';
import { shallow, configure } from 'enzyme';
import Adapter from 'enzyme-adapter-react-16';

configure({ adapter: new Adapter() });

import HelloWorld from './app';

var TestResult = function() {
    this.succeeded = false;
    this.reason = "";
    this.input = "";
    this.expected_output = "";
    this.actual_output = "";
}

export const executeTests = function() {

  var results = [];

  result = new TestResult();
  result.input = 'HelloWorld Component';
  result.expected_output = "span containing text 'Hello World'"

  let wrapper = shallow(<HelloWorld />);

  // Call your Challenge function here.

  let type = wrapper.type();
  let testSuccessful = true;
  let failureReason;

  if (type !== 'span') {
    testSuccessful = false;
    failureReason = "You need to render exactly one span HTML element";
  } else if (wrapper.props().children != "Hello World") {
     testSuccessful = false;
     failureReason = "You have rendered wrong message in your span element";
  }

  result.actual_output = wrapper.html();

  if (testSuccessful) {
    result.succeeded = true;
    result.reason = "Succeeded"
  } else {
    result.succeeded = false;
    result.reason = failureReason;
  }

  results.push(result);

  return results;
}


dlang

React

Dart

GoJS React

Typescript React

Vue.js

## Explanation

In the sum.cpp file:
- Line 5: We declare the function that will sum the values passed in the parameters.

In the main.d file: 
- Line 2: We use `extern (C++)` to link both files and then declare the function in the D program.
- Line 7: We call the sum function and pass the value in the parameters.

>**Note**: To run this program  locally, we have to compile the C++ file separately by using the command `g++ -c sum.cpp` in the terminal and then use the command  `dmd main.d sum.o -L-lstdc++ && ./main`. 




dlang.tar.gz

How to call global functions in C++ from D

Use `extern(C++)` to call C++ global functions from D. Compile C++ separately and link in D.