added some stuff on strings

Examples/src/StringLiteralsAndViews/main_stringLiterals.cpp

@@ -1,26 +1,25 @@
 #include <iostream>
+#include <locale>
 #include <string>
-#include <typeinfo>
 #include <string_view> // since c++17
+#include <typeinfo>
 
 /*! @ brief Function to check if 'text' starts with 'prefix'
-  * 
-  * This function is a simple example of the use of string_view
-  *  @param text the string to be checked
-  *  @param prefix the prefix to be checked
-  *  @return true if 'text' starts with 'prefix', false otherwise
-  */
-bool starts_with(std::string_view text, std::string_view prefix) {
-    return text.substr(0, prefix.size()) == prefix;
+ *
+ * This function is a simple example of the use of string_view
+ *  @param text the string to be checked
+ *  @param prefix the prefix to be checked
+ *  @return true if 'text' starts with 'prefix', false otherwise
+ */
+bool
+starts_with(std::string_view text, std::string_view prefix)
+{
+  return text.substr(0, prefix.size()) == prefix;
 }
 
-
-
 int
 main()
 {
-
-
   // Example of use of raw strings
   std::string interpreted = "Hello\nWorld";
   std::string notInterpreted = R"!(Hello\nWorld)!";
@@ -42,27 +41,58 @@ main()
   // string literals (here I explain only s)
   using namespace std::string_literals;
 
-  // Note that typeid returns two different types. The type name is mangled so not
-  // easily recognizable, but it is certainly different!
+  // Note that typeid returns two different types. The type name is mangled so
+  // not easily recognizable, but it is certainly different!
   auto c = "This is a C-style null terminated string!";
-  std::cout<<c<<std::endl;
-  std::cout<<"The type of c is "<<typeid(c).name()<<std::endl;
+  std::cout << c << std::endl;
+  std::cout << "The type of c is " << typeid(c).name() << std::endl;
   // If you uncomment the next line you get a compilation error.
-  // a C-style string has no method size() (indeed  has no methods at all! is just a char*)
-  //std::cout<<"of length "<<c.size()<<std::endl;
+  // a C-style string has no method size() (indeed  has no methods at all! is
+  // just a char*)
+  // std::cout<<"of length "<<c.size()<<std::endl;
 
   auto s = "This is a C++ string!"s;
-  std::cout<<s<<std::endl;
-  std::cout<<"The type of s is "<<typeid(s).name()<<std::endl;
+  std::cout << s << std::endl;
+  std::cout << "The type of s is " << typeid(s).name() << std::endl;
   // Here we have size since s is a std::string
-  std::cout<<"of length "<<s.size()<<std::endl;
+  std::cout << "of length " << s.size() << std::endl;
 
   // Using string_view you can opearate on string literals without copying them
   // and operate both on C++ and C-style strings without problems
-  // You can operate also on substrings of a string_view with no additional copies
-  // Note that we are mixing c-style strings and c++ strings: string_view is a bridge
-  std::cout<< "Deas '"<<c<<"' start with 'This'?="<<std::boolalpha<<starts_with(c,"This")<<std::endl;
-  std::cout<< "Deas '"<<s<<"' start with 'This'?="<<std::boolalpha<<starts_with(s,"This")<<std::endl;
-  std::cout<< "Deas '"<<trunk<<"' start with 'This'?="<<std::boolalpha<<starts_with(trunk,"This")<<std::endl;
+  // You can operate also on substrings of a string_view with no additional
+  // copies Note that we are mixing c-style strings and c++ strings: string_view
+  // is a bridge Note: you have a lot of utilities to manipulate strings, even
+  // regular expressions!
+  std::cout << "Does '" << c << "' start with 'This'?=" << std::boolalpha
+            << starts_with(c, "This") << std::endl;
+  std::cout << "Does '" << s << "' start with 'This'?=" << std::boolalpha
+            << starts_with(s, "This") << std::endl;
+  std::cout << "Does '" << trunk << "' start with 'This'?=" << std::boolalpha
+            << starts_with(trunk, "This") << std::endl;
+
+  // And now a little experiment (try to understand why)
+  std::cout << "The size of the character e is" << sizeof('e') << std::endl;
+  std::cout << "The size of the character  è is" << sizeof('è') << std::endl;
+  std::cout << "Why??\n";
+  // I store e and è in a char
+  char e_normal{'e'};
+  // char e_accented{'è'}; // this is a multibyte character I get a compiler
+  // error becouse of narrowing
+  char e_accented = 'è'; // Here I have implicit convertion from multibyte (int) to char
+  std::cout << "Printing the characters e and è stored in a char: " << e_normal
+            << " " << e_accented << std::endl;
+  using namespace std::string_literals;
+  std::string e_accented_str = "è"s;
+  std::string e_normal_str = "e"s;
+  std::cout << "Printing the size of a sc++ string storing e and è"
+            << e_normal_str.size() << " " << e_accented_str.size() << std::endl;
+  // the right encoding. 
+
 
+  std::u8string utf8_str = u8"è";// this is a utf-8 string
+  wchar_t e_u8accented = utf8_str[0];// here I extract the character è
+  // that I store in a wchar_t (4 bytes long).
+  std::wcout << L"Printing the character è stored in a wchar_t: " << e_u8accented
+               << std::endl; // but still it does not work
+  return 0;
 }