Updating to C++23

Author: cpp-tutor

headers/01-hellow.cpp

@@ -1,8 +1,8 @@
 // 01-hellow.cpp : prints a line of text to the console
 
-#include <iostream>
+#include <print>
 using namespace std;
 
 int main() {
-    cout << "Hello, World!" << '\n';
+    println("Hello, World!");
 }

headers/01-title.cpp

@@ -1,15 +1,15 @@
 // 01-title.cpp : output the title page of a well-known book
 
-#include <iostream>
+#include <print>
 using namespace std;
 
 int main() {
-    cout << 1+R"(
+    print(1+R"(
                    Alice's
                 Adventures In
                  Wonderland
 
                      by
                 LEWIS CARROLL
-)";
+)");
 }

headers/02-assign.cpp

@@ -1,14 +1,14 @@
 // 02-assign.cpp : assign to local variables
 
-#include <iostream>
+#include <print>
 using namespace std;
 
 int main() {
     int i = 1, j = 2;
     unsigned k;
-    cout << "(1) i = " << i << ", j = " << j << ", k = " << k << '\n';
+    println("(1) i = {}, j = {}, k = {}", i, j, k);
     i = j;
     j = 3;
     k = -1;
-    cout << "(2) i = " << i << ", j = " << j << ", k = " << k << '\n';
+    println("(2) i = {}, j = {}, k = {}", i, j, k);
 }

headers/02-constants.cpp

@@ -1,13 +1,12 @@
 // 02-constants.cpp : introducing the const keyword
 
-#include <iostream>
+#include <print>
 using namespace std;
 
 const double PI = 3.14159265358979;
 
 int main() {
     auto const APPROX_E = 3;
-    cout << "pi is almost exactly " << PI
-    << "e is approximately " << APPROX_E
-    << '\n';
+    println("pi is almost exactly {}, while e is approximately {}",
+        PI, APPROX_E);
 }

headers/02-constexpr.cpp

@@ -1,17 +1,16 @@
 // 02-constexpr.cpp : introducing the constexpr keyword
 
-#include <iostream>
+#include <print>
 #include <cmath>
 using namespace std;
 
-const double PI1 = acos(-1.0);     // acos is not (yet) constexpr
+constexpr double PI1 = acos(-1.0);
 constexpr double PI2 = 22.0 / 7.0;
 
-// the following line does not compile and has been commented out
-//static_assert(PI1 > 3.141 && PI1 < 3.143);
+static_assert(PI1 > 3.141 && PI1 < 3.143);
 static_assert(PI2 > 3.141 && PI2 < 3.143);
 
 int main() {
-    cout << "PI1 = " << PI1 << '\n';
-    cout << "PI2 = " << PI2 << '\n';
+    println("PI1 = {}", PI1);
+    println("PI2 = {}", PI2);
 }

headers/02-height.cpp

@@ -1,6 +1,6 @@
 // 02-height.cpp : define the same variable name in two different namespaces
 
-#include <iostream>
+#include <print>
 using namespace std;
 
 namespace Wonderland {
@@ -12,9 +12,7 @@ namespace VictorianEngland {
 }
 
 int main() {
-    cout << "Alice\'s height varies between "
-    << Wonderland::alice_height_m
-    << "m and "
-    << VictorianEngland::alice_height_m
-    << "m.\n";
+    println("Alice\'s height varies between {}m and {}m",
+        Wonderland::alice_height_m,
+        VictorianEngland::alice_height_m);
 }

headers/02-references.cpp

@@ -1,13 +1,13 @@
 // 02-references.cpp : introducing l-value references
 
-#include <iostream>
+#include <print>
 using namespace std;
 
 int alice_age{ 9 };
 
 int main() {
-    cout << "Alice\'s age is " << alice_age << '\n';
+    println("Alice\'s age is {}", alice_age);
     int& alice_age_ref = alice_age;
     alice_age_ref = 10;
-    cout << "Alice\'s age is now " << alice_age << '\n';
+    println("Alice\'s age is now {}", alice_age);
 }

headers/02-scopes.cpp

@@ -1,16 +1,16 @@
 // 02-scopes.cpp : define three variables with the same name in one program
 
-#include <iostream>
+#include <print>
 using namespace std;
 
 auto a{ 1.5f };
 
 int main() {
-    cout << "(1) " << a << '\n';
+    println("(1) {}", a);
     auto a{ 2u };
-    cout << "(2) " << a << '\n';
+    println("(2) {}", a);
     {
         auto a{ 2.5 };
-        cout << "(3) " << a << '\n';
+        println("(3) {}", a);
     }
 }

headers/02-swap.cpp

@@ -1,13 +1,13 @@
 // 02-swap.cpp : attempt to swap the values of an int and a double
 
-#include <iostream>
+#include <print>
 using namespace std;
 
 int main() {
     int a = 1;
     double b = 2.5;
-    cout << "(1) a = " << a << ", b = " << b << '\n';
+    println("(1) a = {}, b = {}", a, b);
     a = 2.5;
     b = 1;
-    cout << "(2) a = " << a << ", b = " << b << '\n';
+    println("(2) a = {}, b = {}", a, b);
 }

headers/02-uniform.cpp

@@ -1,11 +1,11 @@
 // 02-uniform.cpp : avoid compiler error with uniform initialization and explicit narrowing cast
 
-#include <iostream>
+#include <print>
 using namespace std;
 
 int main() {
     // int c = { 2.5 };                 // Error: this does NOT compile
     int c = { static_cast<int>(2.5) };  // while this does
     double d = { 1 };                   // and so does this
-    cout << "c = " << c << ", d = " << d << '\n';
+    println("c = {}, d = {}", c, d);
 }