x86 movabs r10, 0x123456789abcdef0 49 ba f0 de bc 9a 78 56 34 12Code density uint64_t v = 0x123456789abcdef0; 47 x86 movabs r10, 0x123456789abcdef0 49 ba f0 de bc 9a 78 56 34 12 MIPS li $2, cf 8a 42 34 78 14 02 00 af 26 42 64 b8 14 02 00 f0 de 42 34Code density uint64_t v = 0x123456789abcdef0; 48 x86 movabs r10, 0x123456789abcdef0 49 ba f0 de bc 9a 78 56 34 12 RISC-V li a5, 305418240 cf 8a 42 34 78 14 02 00 af 26 42 64 b8 14 02 00 f0 de 42 34Code density uint64_t v = 0x123456789abcdef0; 49 x86 movabs r10, 0x123456789abcdef0 49 ba f0 de bc 9a 78 56 34 12 RISC-V li a5, 305418240

org/z/8M483Kvba https://godbolt.org/z/czhrT1hhh π https://godbolt.org/z/5aseWr7fz https://godbolt.org/z/nG88rvv5f https://godbolt.org/z/qh4zdzqG6string s3 = (stringstream{} << pi).str(); // 3.14159 org/z/8M483Kvba https://godbolt.org/z/czhrT1hhh π https://godbolt.org/z/5aseWr7fz https://godbolt.org/z/nG88rvv5f https://godbolt.org/z/qh4zdzqG61 2 3 Integer to string #hundreds 1 / 10 / 10 1 2 3 % 1 x . 2 biased exponent 0 normal = ⟹ 000000111 8 ± mantissa 23 biased exponent Binary32 (f) +2 x1 1011000000000000000000 0. 00000011 https://godbolt.org/z/9PGPT9q1E 1 0 0 0 0 0 1 0 0

Quiz 6void f(int* ptr); void f(const int* ptr); int i = 42; const int ci = 42; int make_int() { return 42; } f(i); // ??? f(ci); // ??? f(std::move(i)); // ??? f(std::move(ci)); f(std::move(ci)); // ??? f(42); // ??? f(make_int()); // ??? CppCon 2023 | Forwarding References Quiz: Pointers 7void f(int* ptr); void f(const int* ptr); int i = 42; const int ci = 42; int make_int() make_int() { return 42; } f(i); // ERROR f(ci); // ERROR f(std::move(i)); // ERROR f(std::move(ci)); // ERROR f(42); // ERROR f(make_int()); // ERROR CppCon 2023 | Forwarding

statically typed language Casts allow us to...Why do we need casts?What is a Type? 0x43 0x50 0x50 0x43 0x4F 0x4E 0x21 0x00 Type Value* int[2] {1129336899, 2182735} double 4.81336e-308 float[2] {208.314, 3 17232}, {20047, 33}} char[8] “CPPCON!” *64-bit MSVC v142What is a Type? 0x43 0x50 0x50 0x43 0x4F 0x4E 0x21 0x00 Type Value* int[2] {1129336899, 2182735} double 4.81336e-308 float[2] {208.314, 3 17232}, {20047, 33}} char[8] “CPPCON!” *64-bit MSVC v142What is a Type? 0x43 0x50 0x50 0x43 0x4F 0x4E 0x21 0x00 Type Value* int[2] {1129336899, 2182735} double 4.81336e-308 float[2] {208.314, 3

template F, template typename Functor, typename T> constexpr auto fmap(F f, Functor a) -> FunctorF, T>> { return Functor{f(unwrap(a))}; } (<$>) (<$>) when used as an in�x operator. when used as an in�x operator. fmap :: (a -> b) -> f a -> f b 10HOW TO READ HASKELL SIGNATURES HOW TO READ HASKELL SIGNATURES 11REVIEW: (?) MONADS REVIEW: function returns a functorial value. template F, template typename Functor, typename T> constexpr auto bind(F f, Functor a) -> Functor<...>; 13bind bind IN HASKELL

Dispatch Deleting Functions Name Lookup(Un-)Qualified Name Lookup 16 void f( double ); // (1) namespace N1 { void f( int ); // (2) } // namespace N1 int main() { } // Unqualified // Unqualified lookup; calls (1) // Qualified lookup; calls (2) f( 1.0 ); f( 42 ); N1::f( 42 );(Un-)Qualified Name Lookup 17 void f( double ); // (1) namespace N1 { } // namespace N1 int main() ‘N1’ f( 1.0 ); f( 42 ); N1::f( 42 );(Un-)Qualified Name Lookup 18 void f( double ); // (1) namespace N1 { void f( int ); // (2) void g() { N1::f( 1.0 ); } void h() { f( 1.0

from 49A word about beauty and elegance • Situation: you want to apply a composition of functions f and g to each argument x in a range of values 50A word about beauty and elegance • The intent is begin(v), g); transform(begin(v), end(v), begin(v), f); • … which does two passes through v, with transform(begin(v), end(v), begin(v), f_g_x(f,g)); • … which only does a single pass • … and might template F, class G> auto f_g_x(F f, G g) { return [=](auto && x) { return f(g(x)); }; } 52A word about beauty and elegance template F, class G> auto f_g_x(F f, G g) { return [=](auto

templates  When a compiler encounters an expression like f(x, y, z), it must consider each of these language features to determine which f function to call. 7 Introduction  When used well, these of overloaded functions name put: int put(int c); int put(int c, FILE *f); int put(char const *s); int put(char const *s, FILE *f); 11 Overload Resolution  When the compiler encounters a call to an the function declarations.  For example, // calls... put('a', stdout); // int put(int c, FILE *f); put("Hello\n"); // int put(char const *s); 12Back to Basics - Function Call Resolution Copyright

pointers evolvevoid f(void*) {} void f(char*) {} template auto g(T t) -> decltype(f(t)) { return f(t); } int main() { g(nullptr); }void f(void*) {} void f(char*) {} template template auto g(T t) -> decltype(f(t)) { return f(t); } int main() { g(nullptr); } % clang++ -std=c++20 tests/c++/sfinae-ambiguous.cpp tests/c++/sfinae-ambiguous.cpp:10:5: error: call to 'f' is ambiguous auto g(T t) -> decltype(f(t)) { ^ 1 error generated.% `cwhy --wrapper` -std=c++20 tests/c++/sfinae-ambiguous.cpp void f(void*) {} void f(char*) {}