DEDUCING this PATTERNS BEN DEANE / CPPCON 2021 @ben_deaneOVERVIEW This presentation is about P0847, "Deducing this" ( ) Gašper Ažman, Sy Brand, Ben Deane, Barry Revzin – "We propose a new mechanism mechanism for specifying or deducing the value category of the expression that a member-function is invoked on. In other words, a way to tell from within a member function whether the expression it’s invoked we write) a closure object (the object the compiler generates by evaluating the lambda expression)DEDUCING this AND LAMBDAS First, uniformity of syntax between regular member functions and lambda expressions

writing your own deduction guides • CTAD take down or CTAD sales pitch • PopcornWhat is CTAD ?Deducing function-template template argument template void myFunc(const T&){} myFunc(const T&){} myFunc(1); // deduces T = int, invokes myFunc specialisation Deducing function-template template argumenttemplate void myFunc(const T&){} myFunc(1); myFunc(1); // deduces T = int, invokes myFunc specialisation Template argument deduction Deducing function-template template argumenttemplate struct myStruct { myStruct(const

UDPatomosspace.com | 47 Virtual Functions • ~1986 Curiously Recurring Template Pattern (CRTP) • ~1995 Deducing This • C++23 Timelineatomosspace.com | 48 • Run-Time Polymorphism • Quintessential Object Oriented • C++23 Feature • Simplifies Compile Time Polymorphism New Trend – Explicit Object Parameter/Deducing Thisatomosspace.com | 53 struct NetworkConnection { public: void init(this auto&& self) NetworkConnection { public: void initializeConfig() { // ... } }; New Code – Deducing Thisatomosspace.com | 54 // https://godbolt.org/z/T51xE5qbK struct NetworkConnection { virtual

avoided by delegating to helper methods  Cumbersome  C++23:  Explicit object parameters  deducing this  Replace all 3 overloads with: template auto&& GetName(this Self&& self) a lambda accesses the object that contains the lambda, not the lambda instance itself!  With deducing this: auto fibonacci = [](this auto self, int n) { if (n < 2) { return n; } return self(n

one of my personal incentives for P0847 (Now you see one of my personal incentives for P0847 Deducing Deducing this this)) See also See also C++Weekly Episode 318: My Meetup Got Nerd Sniped! C++Weekly

without frame is in UserSpace@@@ As opposed to library sharing entities with other libraries+ @@@ Deducing this removes the need for CRTP2 Slides1. https://godbolt.org/z/eTznPrno5 @@@ Use default if there’s

Rud Merriam | A Journey into Non-Virtual Polymorphism 41 C++23: Explicit Object Parameter AKA, Deducing This struct Shape { template void draw(this T&& self) { self.draw_impl();}

std::print • Ranges: • to • zip and enumerate • cartesian_product 🕙 Coming next for C++23 • Deducing this (modules support) • 9 remaining C++ STL features ✅ C++98* * with /permissive- ✅ C++11 ✅

getValue() = {}", s.getValue() ); } No template parameter anymore 😊 Explicit object parameter (aka “Deducing This”)The Future of CRTP? 31 So CRTP really just … I guess … goes away.The Future of CRTP? 32The

with the same key always produces a unique cipher text. The idea is to prevent the attacker from deducing information from repeated patterns in the encrypted data. From the provided alternatives, the default