Versions of C++ and the major differences

Modern C++11

• Smartpointers RAII (Resource Acquisition Is Initialization), data / scope driven auto malloc/free
  • Unique: Can't be copied, single object reference, best when possible
  • shared: tracks copies, free when last user out of scope or reset
  • weak: observe, check before ref (may be dangling). use to monitor / avoid circular dependencies.
• std::move to quick copy complex objects to a new owner without actually duplicating the data.
• && rvalue references. Allows hand off of ownership. e.g. from class constructor to main program variable.
• Lambdas e.g. [=i, &str](int tab) { ... } -> String
  • "capture lists" filter the method of reference to non-static scope variables.
    • [], no access to local variables. Everything is in the param list or block
    • [&], reference most commonly used if a variable needs to be modified
    • [=], make a value copy of all local variables used in the lambda
    • etc. combine the above and mention specific variables
  • param ()
  • block {}
  • return type -> trailing, only needed if it can't be inferred.
• auto type is inferred from initializer. No need to re specify component types from a complex type, handy in templates, verifies init and can't cast.
• for (int num : numbers) where numbers is a vector of ints
• constexpr and compile time eval (??)
• more data types in the std library. e.g. array, unordered_map and _set
• thread, mutex, future, atomic (????)

C++17

• destructuring. auto[id, name] = item; //item = {1, "apple"}
• std::optional type (parameter may not be specified)
• std::variant type (may be one of several types)
• std::string_view (??)

C++20

• Concepts to constrain templates (??_)
• Co routines
• Modules
• <=>

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