# Front page snippets for Carbon
## Images
Images are managed in
[Google Drive](https://drive.google.com/drive/folders/1QrBXiy_X74YsOueeC0IYlgyolWIhvusB).
## Quicksort
A sample of quicksort in Carbon.
```cpp
package Sorting;
fn Partition[T:! Comparable & Movable](s: Slice(T))
 -> i64 {
 var i: i64 = -1;
 for (e: T in s) {
 if (e <= s.Last()) { ++i; Swap(&s[i], &e); } } return i; } fn QuickSort[T:! Comparable & Movable](s: Slice(T)) { if (s.Size() <= 1) { return; } let p: i64 = Partition(s); QuickSort(s[:p - 1]); QuickSort(s[p + 1:]); } ``` ## Carbon and C++ ### C++ ```cpp // C++: #include <numbers>
#include <print>
#include <span>
#include <stdfloat>
#include <vector>
// or: import std;
struct Circle {
 std::float32_t r;
};
void PrintTotalArea(std::span<circle> circles) {
 std::float32_t area = 0;
 for (const Circle& c : circles) {
 area += std::numbers::pi * c.r * c.r;
 }
 std::print("Total area: {}\n", area);
}
auto main() -> int {
 std::vector<circle> circles = {{.r = 1.0}, {.r = 2.0}};
 // Implicitly converts `vector` to `span`.
 PrintTotalArea(circles);
 return 0;
}
```
### Carbon
```cpp
// Carbon:
package Geometry;
import Math;
class Circle {
 var r: f32;
}
fn PrintTotalArea(circles: [Circle]) {
 var area: f32 = 0;
 for (c: Circle in circles) {
 area += Math.Pi * c.r * c.r;
 }
 Print("Total area: {0}", area);
}
fn Main() -> i32 {
 // A dynamically sized array, like `std::vector`.
 var circles: array [Circle] = ({.r = 1.0}, {.r = 2.0});
 // Implicitly constructs a slice from the array.
 PrintTotalArea(circles);
 return 0;
}
```
### Mixed
```cpp
// C++ code used in both Carbon and C++:
#include <stdfloat>
struct Circle {
 std::float32_t r;
};
// Carbon exposing a function for C++:
package Geometry;
import Cpp library "circle.h";
import Math;
fn PrintTotalArea(circles: [Cpp.Circle]) {
 var area: f32 = 0;
 for (c: Cpp.Circle in circles) {
 area += Math.Pi * c.r * c.r;
 }
 Print("Total area: {0}", area);
}
// C++ calling Carbon:
#include <vector>
#include "circle.h"
#include "geometry.carbon.h"
auto main() -> int {
 std::vector<circle> circles = {{1.0}, {2.0}};
 // A Carbon slice supports implicit construction
 // from `std::vector`, similar to `std::span`.
 Geometry::PrintTotalArea(circles);
 return 0;
}
```
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