Learn D with Real Code Examples

import std.stdio;

int count = 0;
bool isDark = false;

void updateUI() {
    writeln("Counter: ", count);
    writeln("Theme: ", isDark ? "Dark" : "Light");
}

void increment() {
    count += 1;
    updateUI();
}

void decrement() {
    count -= 1;
    updateUI();
}

void reset() {
    count = 0;
    updateUI();
}

void toggleTheme() {
    isDark = !isDark;
    updateUI();
}

// Simulate actions
updateUI();
increment();
increment();
toggleTheme();
decrement();
reset();

Demonstrates a simple counter with theme toggling using D variables and console output.

import std.stdio;
void main() {
    int a = 10;
    int b = 20;
    int sum = a + b;
    writeln("Sum: ", sum);
}

Adds two numbers and prints the result.

import std.stdio;
int factorial(int n) {
    return n <= 1 ? 1 : n * factorial(n - 1);
}
void main() {
    writeln("Factorial 5: ", factorial(5));
}

Calculates factorial recursively.

import std.stdio;
int fib(int n) {
    return n < 2 ? n : fib(n - 1) + fib(n - 2);
}
void main() {
    foreach(i; 0 .. 10)
        writeln(fib(i));
}

Generates first 10 Fibonacci numbers.

import std.stdio;
void main() {
    int a = 10, b = 20;
    int max = a > b ? a : b;
    writeln("Max: ", max);
}

Finds the maximum of two numbers.

import std.stdio;
void main() {
    int[] arr = [1,2,3,4,5];
    int sum = 0;
    foreach(x; arr)
        sum += x;
    writeln("Sum: ", sum);
}

Sums elements of an array.

import std.stdio;
void main() {
    int[] arr = [1,2,3,4,5];
    foreach(x; arr)
        if(x % 2 == 0)
        writeln(x);
}

Prints even numbers from an array.

import std.stdio;
void main() {
    int count = 3;
    if(count < 5)
        count++;
    writeln("Count: ", count);
}

Increment counter only if less than 5.

import std.stdio;
void main() {
    int count = 0;
    count += 1;
    count += 1;
    writeln("Count: ", count);
    count = 0;
    writeln("Count: ", count);
}

Counter that increments and can be reset.

import std.stdio;
void main() {
    bool isDark = false;
    writeln("Theme: ", isDark ? "Dark" : "Light");
    isDark = !isDark;
    writeln("Theme: ", isDark ? "Dark" : "Light");
    isDark = !isDark;
    writeln("Theme: ", isDark ? "Dark" : "Light");
}

Toggles theme multiple times.