String manipulations

C++ :

#include <iostream>
#include <string>
#include <sstream>
#include <algorithm>

using namespace std;

int main ()
{
    // string concatenation
    string salute = "Hello";
    string name = "world";
    string greeting = salute + " " + name;
    greeting += '!';
    cout << greeting << endl;

    // to upper
    string str = greeting;
    transform(str.begin(), str.end(), str.begin(), ::toupper);
    cout << str << endl;

    // to lower
    str = greeting;
    transform(str.begin(), str.end(), str.begin(), ::tolower);
    cout << str << endl;

    // string format
    int a = 1;
    int b = 2;
    int c = a + b;

    ostringstream os;
    os << "The sum of " << a << " and " << b << " is " << c;    
    cout << os.str() << endl; 

    string s1 ("There are two objects on the table, the 1st object is a book, the 2nd object is a pen.");
    string s2 ("object");

    // get character at a position
    char ch = s1[6];
    cout << ch << endl;

    // substring
    string s3 = s1.substr(10, 11);
    cout << s3 << endl;

    // string replace
    string s4 = s3.replace(0, 3, "three");
    cout << s4 << endl;

    // string find
    size_t found = s1.find(s2);
    if (found!=string::npos)
        cout << "first 'object' found at: " << found << endl;

    // string reverse find
    found = s1.rfind(s2);
    if (found!=string::npos)
        cout << "last 'object' found at: " << found << endl;

    return 0;
}

Rust :

fn main()
{
    // string concatenation
    let salute = "Hello";
    let name = "world";
    let mut greeting_string : String = salute.to_owned() + " " + name;
    greeting_string.push('!');
    let greeting :&str = &greeting_string;
    println!("{}", greeting);

    // upper case
    println!("{}", greeting_string.to_uppercase());

    // lower case
    println!("{}", greeting_string.to_lowercase());

    // string format
    let a = 1;
    let b = 2;
    let c = a + b;
    let tmp_string : String = format!("The sum of {} and {} is {}", a, b, c);
    let s : &str = &tmp_string;
    println!("{}", s);

    let s1 = "There are two objects on the table, the 1st object is a book, the 2nd object is a pen.";
    let s2 = "object";

    // get character at a position
    let ch = s1.chars().nth(6).unwrap();
    println!("{}", ch);

    // substring
    let s3 = &s1.chars().skip(10).take(11).collect::<String>();
    // For ascii string , you can use : let s3 = &s1[10..21];
    println!("{}", s3);

    // string replace
    let s4 = str::replace(s3, "two", "three");
    println!("{}", s4);

    // string find
    if let Some(found) = s1.find(s2) 
    {
        println!("first 'object' found at: {}", found);
    }

    // string reverse find
    if let Some(found) = s1.rfind(s2)
    {
        println!("last 'object' found at: {}", found);
    }    
}

As stated in chapter "Basic data types", Rust has two types of string : the raw string &str , and the object String.

The operator + only works for String and does not work for &str, therefore in order to concatenate several raw strings &str, we need to convert the first of them into an object String and then apply the + operator to the remained items.

To convert from &str to String :

let greeting_string : String = salute.to_owned()

To convert from String to &str :

let greeting :&str = &greeting_string;