org/z/6PdebYn1K) (*) 5. https://fmt.dev/latest/api.html#formatting-user-defined-types7 Slides1. Namespaces ordering: https://godbolt.org/z/qvMcYn1Kd (if in both the namespace and the argument’s namespace) redeclarations are only allowed • after the point of declaration, • at namespace scope, and • in namespaces that enclose the original namespace (including the global namespace). Also, they must use qualified-id Improvement of usage: https://godbolt.org/z/qnnEbf3qo @@@ Now we can move implementations across namespaces, in a non-intrusive way1 Slides@@@ All templates can be constrained with concepts1 Slides1. @@@

of functions. Towards the end of this talk, we will talk about grouping related functions (into namespaces) and as member functions in classes. Within our discussion of functions in classes, we'll touch function at some point in a large enough project) ○ Refactoring becomes easier as well. ■ If nested namespaces were to get too long -- at a local scope you can use: ● using namespace mike; ● (Note: I recommend Object-Oriented Programming 67Object-Oriented (Actions + Attributes) ● Beyond grouping functions into namespaces ● We can group related functions and data together to form a new user-defined data type -- an

cheap (to copy) range adaptor: make a range into a view 3 . 2mechanics - headers, namespaces mechanics - headers, namespaces #include // new header for ranges and views namespace std { namespace

lookup (ADL) [basic.lookup.argdep] • “When [a func`on is called via] an unqualified-id, other namespaces not considered [by UNL] may be searched, and … declara`ons not otherwise visible may be found so we call it. ➁ (g) is an expression, not an unqualified-id, due to the parens, so no other namespaces are searched. UNL hadn’t found a suitable function decl, so the call is ill-formed. 35 Qualified

functions and data in C object files, and vice versa • The C language does not provide overloading or namespaces • Given a C function whose declaration is void fubar(int), • The corresponding symbol name in 2020 Bob Steagall K E W B C O M P U T I N G Name Mangling • C++ does support overloading and namespaces – names can be reused • A C++ entity name is mapped into a name that can co-exist with C entity

a template argument, to the operator instantiation. 10/26/21 Pablo Halpern, 2021 (CC BY 4.0) 17Namespaces for literals ■ UDL operators are looked up using ordinary name lookup, no namespace qualifiers ■ To avoid collisions between similar UDL suffixes, UDL operators are usually put in their own namespaces and imported with using directives: 10/26/21 Pablo Halpern, 2021 (CC BY 4.0) 18 namespace temperature_literals

Use the proper context for your code ● Use namespaces properly to give context to your code, including hidden “detail” and unnamed (anonymous) namespaces. ● Use nested type: put types (classes, enums

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and the Vector Graphics API ❏ Declarations and Type Conversions ❏ C++ ISO Standard ❏ Inline Namespaces ❏ Lambdas in Action ❏ Any Optional ❏ Variant ❏ CsPaint Library ❏ Moving to C++17 ❏ What

names ● Name collision prevention ○ i.e., names like job, build, util, etc. ○ Name registry? Namespaces? ● Consistent name spellings across the ecosystem ○ ✖ Different names for different package managers