NDC{TechTown} Type Safe C++? - LOL! :-)

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 1/119 Type Safe C++? - LOL! :-) Björn Fahller

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 2/119 Type Safe C++? - LOL! :-) Björn Fahller

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 3/119 Type Safe C++? - LOL! :-) What is type safety?

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 4/119 What is type safety? type safety (Noun) the extent to which a programming language discourages or prevents type errors -- Wiktionary

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 5/119 A type safe system discourages or prevents... ● ... use of one type when another is intended ● ... operations that do not make sense ● ... use of values outside the defined space

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 6/119 ● Introduction to type safety ● Type safety in C++ ● Simple library solution for strong types ● Sophisticated libraries – scouting github! ● What strong types does with your code Type Safe C++? - LOL! :-)

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 7/119 using request_id = uint32_t; using receiver_id = uint32_t; token remove(request_id req, receiver_id rec); token initiate_remove(receiver_id receiver) { auto req = new_request(); return remove(receiver, req); } My story begins

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 8/119 using request_id = uint32_t; using receiver_id = uint32_t; token remove(request_id req, receiver_id rec); token initiate_remove(receiver_id receiver) { auto req = new_request(); return remove(receiver, req); } My story begins

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 9/119 using request_id = uint32_t; using receiver_id = uint32_t; token remove(request_id req, receiver_id rec); token initiate_remove(receiver_id receiver) { auto req = new_request(); return remove(receiver, req); } My story begins

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 10/119 void other(A const& a); void func(B b) { other(b); } When is this call allowed?

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 11/119 struct A { int value; }; struct B { int value; }; void other(A const& a); void func(B b) { other(b); }

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 12/119 struct A { int value; }; struct B { int value; }; void other(A const& a); void func(B b) { other(b); } If we want this to compile, we can add:

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 13/119 struct A { int value; }; struct B { int value; }; void other(A const& a); void func(B b) { other(b); } If we want this to compile, we can add: A::A(B const&); // not explicit

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 14/119 struct A { int value; }; struct B { int value; }; void other(A const& a); void func(B b) { other(b); } If we want this to compile, we can add: A::A(B const&); // not explicit B::operator A(); // not explicit

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 15/119 struct A { int value; }; struct B { int value; }; void other(A const& a); void func(B b) { other(b); } If we want this to compile, we can add: A::A(B const&); // not explicit B::operator A(); // not explicit A as a public base class to B

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 16/119 struct request_id { uint32_t value; }; struct receiver_id { uint32_t value; }; token remove(request_id req, receiver_id rec); token initiate_remove(receiver_id receiver) { request_id req = new_request(); return remove(receiver, req); } A different story begins

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 17/119 struct request_id { uint32_t value; }; struct receiver_id { uint32_t value; }; token remove(request_id req, receiver_id rec); token initiate_remove(receiver_id receiver) { request_id req = new_request(); return remove(receiver, req); } error: no matching function for call to 'remove' return remove(receiver, req); ^~~~~~ note: candidate function not viable: no known conversion from 'receiver_id' to 'request_id' for 1st argument token remove(request_id req, receiver_id rec); ^

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 18/119 We have control over when the compiler will allow a conversion!

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 19/119 class receiver_id { public: explicit receiver_id(uint32_t v) : value{v} {} operator uint32_t() const { return value; } private: uint32_t value; };

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 20/119 class receiver_id { public: explicit receiver_id(uint32_t v) : value{v} {} operator uint32_t() const { return value; } bool operator==(receiver_id v) const { return value == v.value; } bool operator!=(receiver_id v) const; private: uint32_t value; };

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 21/119 class receiver_id { public: explicit receiver_id(uint32_t v) : value{v} {} operator uint32_t() const { return value; } bool operator==(receiver_id v) const { return value == v.value; } bool operator!=(receiver_id v) const; bool operator<(receiver_id v) const; ... private: uint32_t value; };

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 22/119 class receiver_id { public: explicit receiver_id(uint32_t v) : value{v} {} operator uint32_t() const { return value; } bool operator==(receiver_id v) const { return value == v.value; } bool operator!=(receiver_id v) const; bool operator<(receiver_id v) const; ... private: uint32_t value; }; There’s an awful lot of boiler plate code here!

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 23/119 class receiver_id { public: explicit receiver_id(uint32_t v) : value{v} {} operator uint32_t() const { return value; } bool operator==(receiver_id v) const { return value == v.value; } bool operator!=(receiver_id v) const; bool operator<(receiver_id v) const; ... private: uint32_t value; }; There’s an awful lot of boiler plate code here! Repeat once more for request_id

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 24/119 ● Introduction to type safety ● Type safety in C++ ● Simple library solution for strong types ● Sophisticated libraries – scouting github! ● What strong types does with your code Type Safe C++? - LOL! :-)

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 25/119 template class safe_type { public: private: T value_; };

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 26/119 template class safe_type { public: safe_type(T t) : value_(std::move(t)) {} operator T() const { return value_; } // operators... private: T value_; };

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 27/119 template class safe_type { public: safe_type(T t) : value_(std::move(t)) {} template safe_type(safe_type const&) = delete; operator T() const { return value_; } // operators... private: T value_; };

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 28/119 template class safe_type { public: safe_type(T t) : value_(std::move(t)) {} template safe_type(safe_type const&) = delete; operator T() const { return value_; } // operators... private: T value_; }; using int1 = safe_type; using int2 = safe_type;

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 29/119 using request_id = safe_type; using receiver_id = safe_type; token remove(request_id req, receiver_id rec); token initiate_remove(receiver_id receiver) { auto req = new_request(); return remove(receiver, req); }

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 30/119 using request_id = safe_type; using receiver_id = safe_type; token remove(request_id req, receiver_id rec); token initiate_remove(receiver_id receiver) { auto req = new_request(); return remove(receiver, req); }

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 31/119 using request_id = safe_type; using receiver_id = safe_type; token remove(request_id req, receiver_id rec); token initiate_remove(receiver_id receiver) { auto req = new_request(); return remove(receiver, req); }

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 32/119 using request_id = safe_type; using receiver_id = safe_type; token remove(request_id req, receiver_id rec); token initiate_remove(receiver_id receiver) { auto req = new_request(); return remove(receiver, req); } error: no matching function for call to 'remove' remove(receiver, req); ^~~~~~ note: candidate function not viable: no known conversion from 'safe_type<[...], struct receiver_id_tag>' to 'safe_type<[...], struct request_id_tag>' for 1st argument token remove(request_id req, receiver_id rec); ^

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 33/119 using request_id = safe_type; using receiver_id = safe_type; token remove(request_id req, receiver_id rec); token initiate_remove(receiver_id receiver) { auto req = new_request(); return remove(receiver, req); }

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 34/119 struct request_id : safe_type { using safe_type::safe_type; }; struct receiver_id : safe_type { using safe_type::safe_type; }; token remove(request_id req, receiver_id rec); token initiate_remove(receiver_id receiver) { auto req = new_request(); return remove(receiver, req); }

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 35/119 struct request_id : safe_type { using safe_type::safe_type; }; struct receiver_id : safe_type { using safe_type::safe_type; }; token remove(request_id req, receiver_id rec); token initiate_remove(receiver_id receiver) { auto req = new_request(); return remove(receiver, req); } error: no matching function for call to 'remove' remove(receiver, req); ^~~~~~ note: candidate function not viable: no known conversion from 'receiver_id' to 'request_id' for 1st argument token remove(request_id req, receiver_id rec); ^

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 36/119 struct request_id : safe_type { using safe_type::safe_type; }; struct receiver_id : safe_type { using safe_type::safe_type; }; token remove(request_id req, receiver_id rec); token initiate_remove(receiver_id receiver) { auto req = new_request(); return remove(receiver, req); } #define SAFE_TYPE(name, base_type) \ struct name : safe_type { \ using safe_type::safe_type; \ }

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 37/119 SAFE_TYPE(request_id, uint32_t); SAFE_TYPE(receiver_id, uint32_t); token remove(request_id req, receiver_id rec); token initiate_remove(receiver_id receiver) { auto req = new_request(); return remove(receiver, req); } #define SAFE_TYPE(name, base_type) \ struct name : safe_type { \ using safe_type::safe_type; \ }

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 38/119 ● Introduction to type safety ● Type safety in C++ ● Simple library solution for strong types ● Sophisticated libraries – scouting github! ● What strong types does with your code Type Safe C++? - LOL! :-)

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 39/119 Jonathan Müller @foonathan type_safe Zero overhead utilities for preventing bugs at compile time https://github.com/foonathan/type_safe

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 40/119 Jonathan Müller @foonathan type_safe Zero overhead utilities for preventing bugs at compile time https://github.com/foonathan/type_safe A rich type library, with which you can piece together the exact behaviour of a type that you want. It also includes a number of predefined neat type templates, and other features like improved optional and variant

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 41/119 // type_safe/strong_typedef.hpp template class type_safe::strong_typedef { public: constexpr strong_typedef(); explicit constexpr strong_typedef(const T& value); explicit constexpr strong_typedef(T&& value); explicit constexpr operator T&() & noexcept; explicit constexpr operator const T&() const & noexcept; explicit constexpr operator T&&() && noexcept; explicit constexpr operator const T&&() const && noexcept; }; https://github.com/foonathan/type_safe

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 42/119 https://github.com/foonathan/type_safe #include

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 43/119 https://github.com/foonathan/type_safe #include namespace ts = type_safe;

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 44/119 https://github.com/foonathan/type_safe #include namespace ts = type_safe; struct my_handle : ts::strong_typedef { using strong_typedef::strong_typedef; };

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 45/119 https://github.com/foonathan/type_safe #include namespace ts = type_safe; namespace op = type_safe::strong_typedef_op; struct my_handle : ts::strong_typedef { using strong_typedef::strong_typedef; };

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 46/119 https://github.com/foonathan/type_safe #include namespace ts = type_safe; namespace op = type_safe::strong_typedef_op; struct my_handle : ts::strong_typedef , op::equality_comparison { using strong_typedef::strong_typedef; };

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 47/119 https://github.com/foonathan/type_safe #include namespace ts = type_safe; namespace op = type_safe::strong_typedef_op; struct my_handle : ts::strong_typedef , op::equality_comparison , op::output_operator { using strong_typedef::strong_typedef; };

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 48/119 https://github.com/foonathan/type_safe #include namespace ts = type_safe; namespace op = type_safe::strong_typedef_op; struct my_handle : ts::strong_typedef , op::equality_comparison , op::output_operator { using strong_typedef::strong_typedef; }; struct my_int : ts::strong_typedef , op::integer_arithmetic { using strong_typedef::strong_typedef; };

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 49/119 https://github.com/foonathan/type_safe #include namespace ts = type_safe; namespace op = type_safe::strong_typedef_op; struct my_handle : ts::strong_typedef , op::equality_comparison { using strong_typedef::strong_typedef; friend std::ostream& operator<<(std::ostream& os, my_handle const& h) { return os << "H{" << static_cast(h) << "}"; } };

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 50/119 https://github.com/foonathan/type_safe #include namespace ts = type_safe; namespace op = type_safe::strong_typedef_op; struct my_handle : ts::strong_typedef , op::equality_comparison { using strong_typedef::strong_typedef; friend std::ostream& operator<<(std::ostream& os, my_handle const& h) { return os << "H{" << ts::get(h) << "}"; } };

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 51/119 Jonathan Boccara @joboccara NamedType Implementation of strong types in C++ https://github.com/joboccara/NamedType

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 52/119 Jonathan Boccara @joboccara NamedType Implementation of strong types in C++ https://github.com/joboccara/NamedType A small type library with a simpler aim, but which still allows you to piece together the strong types with your desired behaviour. It also supports conversions between different types of the same kind, for example meters to feet, or non-linear like Watt to dB.

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 53/119 Jonathan Boccara @joboccara NamedType Implementation of strong types in C++ https://github.com/joboccara/NamedType A small type library with a simpler aim, but which still allows you to piece together the strong types with your desired behaviour. It also supports conversions between different types of the same kind, for example meters to feet, or non-linear like Watt to dB. MeetingC++ https://www.youtube.com/watch?v=WVleZqzTw2k

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 54/119 #include using my_handle = fluent::NamedType< int, struct my_handle_tag >; https://github.com/joboccara/NamedType

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 55/119 #include using my_handle = fluent::NamedType< int, struct my_handle_tag, fluent::comparable, fluent::printable, fluent::hashable >; https://github.com/joboccara/NamedType

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 56/119 #include struct my_handle : fluent::NamedType< int, my_handle, fluent::comparable, fluent::printable, fluent::hashable > { using NamedType::NamedType; }; https://github.com/joboccara/NamedType

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 57/119 #include struct my_handle : fluent::NamedType< int, my_handle, fluent::comparable, fluent::printable, fluent::hashable, fluent::ImplicitlyConvertibleTo::templ > { using NamedType::NamedType; }; https://github.com/joboccara/NamedType

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 58/119 ● Introduction to type safety ● Type safety in C++ ● Simple library solution for strong types ● Sophisticated libraries – scouting github! ● What strong types does with your code Type Safe C++? - LOL! :-)

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 59/119 Network capacity utilisation 0 1 2 3 4 5 6 7 8 9 10 11 121314151617181920212223 Frame with 24 slots A slot is a network capacity quanta

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 60/119 Network capacity utilisation 0 1 2 3 4 5 6 7 8 9 10 11 121314151617181920212223 Frame with 24 slots SlotCount SlotIndexes SlotRanges 8 3,4,7,8,13,14,15,16 {3-4},{7-8},{13-16} 3 5,9,10 {5},{9-10} 13 0,1,2,6,11,12,17,18, 19,20,21,22,23 {0-2},{6},{11-12},{17-23} A slot is a network capacity quanta

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 61/119 Network capacity utilisation 0 1 2 3 4 5 6 7 8 9 10 11 121314151617181920212223 Frame with 24 slots SlotCount SlotIndexes SlotRanges 8 3,4,7,8,13,14,15,16 {3-4},{7-8},{13-16} 3 5,9,10 {5},{9-10} 13 0,1,2,6,11,12,17,18, 19,20,21,22,23 {0-2},{6},{11-12},{17-23} A slot is a network capacity quanta typename SlotIndex; typename SlotCount; struct SlotRange{ SlotIndex start; SlotCount length; };

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 62/119 Magic Numbers

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 63/119 Connection createConnection(Address destination, SlotCount capacity); Connection createSDI_Connection(Address destination) { return createConnection(destination, 528); }

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 64/119 Connection createConnection(Address destination, SlotCount capacity); Connection createSDI_Connection(Address destination) { return createConnection(destination, SlotCount{528}); }

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 65/119 Connection createConnection(Address destination, SlotCount capacity); constexpr SlotCount SDI_Capacity{528}; Connection createSDI_Connection(Address destination) { return createConnection(destination, SDI_Capacity); }

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 66/119 Encapsulation

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 67/119 class MessageBuffer { public: template void serialize_bits(unsigned value); }; SlotCount capacity = ... MessageBuffer buffer ... buffer.serialize_bits<24>(capacity);

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 68/119 class MessageBuffer { public: template void serialize_bits(unsigned value); }; SlotCount capacity = ... MessageBuffer buffer ... buffer.serialize_bits<24>(capacity);

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 69/119 class MessageBuffer { public: template void serialize_bits(unsigned value); }; void serialize_data(MessageBuffer& b, SlotCount const& c) { b.serialize_bits<24>(c); } SlotCount capacity = ... MessageBuffer buffer ... serialize_data(buffer, capacity);

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 70/119 class MessageBuffer { public: template void serialize(T const& t) { serialize_data(*this, t); } template void serialize_bits(unsigned value); }; void serialize_data(MessageBuffer& b, SlotCount const& c) { b.serialize_bits<24>(c); } SlotCount capacity = ... MessageBuffer buffer ... buffer.serialize(capacity);

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 71/119 Type Semantics

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 72/119 class SlotPool { public: void releaseCapacity(std::vector const& ranges) SlotCount availableCapacity() const { return unusedSlots;} ... private: SlotCount unusedSlots; ... };

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 73/119 class SlotPool { public: void releaseCapacity(std::vector const& ranges) { for (auto& range : ranges) { unusedSlots += range.length; } ... } SlotCount availableCapacity() const { return unusedSlots;} ... private: SlotCount unusedSlots; ... };

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 74/119 class SlotPool { public: void releaseCapacity(std::vector const& ranges) { for (auto& range : ranges) { unusedSlots += range.length; } ... } SlotCount availableCapacity() const { return unusedSlots;} ... private: SlotCount unusedSlots; ... }; Does not compile! No operator += for SlotCount

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 75/119 Which operations makes sense? SlotCount+SlotCount? 0 1 2 3 4 5 6 7 8 9 10 11 121314151617181920212223 Frame with 24 slots

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 76/119 Which operations makes sense? SlotCount+SlotCount->SlotCount 0 1 2 3 4 5 6 7 8 9 10 11 121314151617181920212223 Frame with 24 slots

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 86/119 Which operations makes sense? SlotCount+SlotCount->SlotCount SlotCount-SlotCount->SlotCount SlotCount*SlotCount SlotCount*Ratio->SlotCount SlotCount/SlotCount->Ratio SlotCount/Ratio->SlotCount 0 1 2 3 4 5 6 7 8 9 10 11 121314151617181920212223 Frame with 24 slots

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 89/119 Which operations makes sense? SlotCount+SlotCount->SlotCount SlotCount-SlotCount->SlotCount SlotCount*SlotCount SlotCount*Ratio->SlotCount SlotCount/SlotCount->Ratio SlotCount/Ratio->SlotCount SlotIndex+SlotIndex SlotIndex+SlotCount? 0 1 2 3 4 5 6 7 8 9 10 11 121314151617181920212223 Frame with 24 slots

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 92/119 Which operations makes sense? SlotCount+SlotCount->SlotCount SlotCount-SlotCount->SlotCount SlotCount*SlotCount SlotCount*Ratio->SlotCount SlotCount/SlotCount->Ratio SlotCount/Ratio->SlotCount SlotIndex+SlotIndex SlotIndex+SlotCount->SlotIndex SlotIndex-SlotIndex->SlotCount 0 1 2 3 4 5 6 7 8 9 10 11 121314151617181920212223 Frame with 24 slots

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 93/119 Which operations makes sense? SlotCount+SlotCount->SlotCount SlotCount-SlotCount->SlotCount SlotCount*SlotCount SlotCount*Ratio->SlotCount SlotCount/SlotCount->Ratio SlotCount/Ratio->SlotCount SlotIndex+SlotIndex SlotIndex+SlotCount->SlotIndex SlotIndex-SlotIndex->SlotCount SlotIndex/SlotIndex? 0 1 2 3 4 5 6 7 8 9 10 11 121314151617181920212223 Frame with 24 slots

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 94/119 Which operations makes sense? SlotCount+SlotCount->SlotCount SlotCount-SlotCount->SlotCount SlotCount*SlotCount SlotCount*Ratio->SlotCount SlotCount/SlotCount->Ratio SlotCount/Ratio->SlotCount SlotIndex+SlotIndex SlotIndex+SlotCount->SlotIndex SlotIndex-SlotIndex->SlotCount SlotIndex/SlotIndex 0 1 2 3 4 5 6 7 8 9 10 11 121314151617181920212223 Frame with 24 slots

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 96/119 Which operations makes sense? SlotCount+SlotCount->SlotCount SlotCount-SlotCount->SlotCount SlotCount*SlotCount SlotCount*Ratio->SlotCount SlotCount/SlotCount->Ratio SlotCount/Ratio->SlotCount SlotIndex+SlotIndex SlotIndex+SlotCount->SlotIndex SlotIndex-SlotIndex->SlotCount SlotIndex/SlotIndex SlotIndex/SlotCount 0 1 2 3 4 5 6 7 8 9 10 11 121314151617181920212223 Frame with 24 slots

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 97/119 Which operations makes sense? SlotCount+SlotCount->SlotCount SlotCount-SlotCount->SlotCount SlotCount*SlotCount SlotCount*Ratio->SlotCount SlotCount/SlotCount->Ratio SlotCount/Ratio->SlotCount SlotIndex+SlotIndex SlotIndex+SlotCount->SlotIndex SlotIndex-SlotIndex->SlotCount SlotIndex/SlotIndex SlotIndex/SlotCount SlotIndex/Ratio? 0 1 2 3 4 5 6 7 8 9 10 11 121314151617181920212223 Frame with 24 slots

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 98/119 Which operations makes sense? SlotCount+SlotCount->SlotCount SlotCount-SlotCount->SlotCount SlotCount*SlotCount SlotCount*Ratio->SlotCount SlotCount/SlotCount->Ratio SlotCount/Ratio->SlotCount SlotIndex+SlotIndex SlotIndex+SlotCount->SlotIndex SlotIndex-SlotIndex->SlotCount SlotIndex/SlotIndex SlotIndex/SlotCount SlotIndex/Ratio 0 1 2 3 4 5 6 7 8 9 10 11 121314151617181920212223 Frame with 24 slots

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 99/119 Which operations makes sense? SlotCount+SlotCount->SlotCount SlotCount-SlotCount->SlotCount SlotCount*SlotCount SlotCount*Ratio->SlotCount SlotCount/SlotCount->Ratio SlotCount/Ratio->SlotCount SlotIndex+SlotIndex SlotIndex+SlotCount->SlotIndex SlotIndex-SlotIndex->SlotCount SlotIndex/SlotIndex SlotIndex/SlotCount SlotIndex/Ratio SlotIndex*SlotIndex? 0 1 2 3 4 5 6 7 8 9 10 11 121314151617181920212223 Frame with 24 slots

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 100/119 Which operations makes sense? SlotCount+SlotCount->SlotCount SlotCount-SlotCount->SlotCount SlotCount*SlotCount SlotCount*Ratio->SlotCount SlotCount/SlotCount->Ratio SlotCount/Ratio->SlotCount SlotIndex+SlotIndex SlotIndex+SlotCount->SlotIndex SlotIndex-SlotIndex->SlotCount SlotIndex/SlotIndex SlotIndex/SlotCount SlotIndex/Ratio SlotIndex*SlotIndex 0 1 2 3 4 5 6 7 8 9 10 11 121314151617181920212223 Frame with 24 slots

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 101/119 Which operations makes sense? SlotCount+SlotCount->SlotCount SlotCount-SlotCount->SlotCount SlotCount*SlotCount SlotCount*Ratio->SlotCount SlotCount/SlotCount->Ratio SlotCount/Ratio->SlotCount SlotIndex+SlotIndex SlotIndex+SlotCount->SlotIndex SlotIndex-SlotIndex->SlotCount SlotIndex/SlotIndex SlotIndex/SlotCount SlotIndex/Ratio SlotIndex*SlotIndex SlotIndex*SlotCount? 0 1 2 3 4 5 6 7 8 9 10 11 121314151617181920212223 Frame with 24 slots

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 102/119 Which operations makes sense? SlotCount+SlotCount->SlotCount SlotCount-SlotCount->SlotCount SlotCount*SlotCount SlotCount*Ratio->SlotCount SlotCount/SlotCount->Ratio SlotCount/Ratio->SlotCount SlotIndex+SlotIndex SlotIndex+SlotCount->SlotIndex SlotIndex-SlotIndex->SlotCount SlotIndex/SlotIndex SlotIndex/SlotCount SlotIndex/Ratio SlotIndex*SlotIndex SlotIndex*SlotCount 0 1 2 3 4 5 6 7 8 9 10 11 121314151617181920212223 Frame with 24 slots

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 103/119 Which operations makes sense? SlotCount+SlotCount->SlotCount SlotCount-SlotCount->SlotCount SlotCount*SlotCount SlotCount*Ratio->SlotCount SlotCount/SlotCount->Ratio SlotCount/Ratio->SlotCount SlotIndex+SlotIndex SlotIndex+SlotCount->SlotIndex SlotIndex-SlotIndex->SlotCount SlotIndex/SlotIndex SlotIndex/SlotCount SlotIndex/Ratio SlotIndex*SlotIndex SlotIndex*SlotCount SlotIndex*Ratio? 0 1 2 3 4 5 6 7 8 9 10 11 121314151617181920212223 Frame with 24 slots

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 104/119 Which operations makes sense? SlotCount+SlotCount->SlotCount SlotCount-SlotCount->SlotCount SlotCount*SlotCount SlotCount*Ratio->SlotCount SlotCount/SlotCount->Ratio SlotCount/Ratio->SlotCount SlotIndex+SlotIndex SlotIndex+SlotCount->SlotIndex SlotIndex-SlotIndex->SlotCount SlotIndex/SlotIndex SlotIndex/SlotCount SlotIndex/Ratio SlotIndex*SlotIndex SlotIndex*SlotCount SlotIndex*Ratio 0 1 2 3 4 5 6 7 8 9 10 11 121314151617181920212223 Frame with 24 slots

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 105/119 Which operations makes sense? SlotCount+SlotCount->SlotCount SlotCount-SlotCount->SlotCount SlotCount*SlotCount SlotCount*Ratio->SlotCount SlotCount/SlotCount->Ratio SlotCount/Ratio->SlotCount SlotIndex+SlotIndex SlotIndex+SlotCount->SlotIndex SlotIndex-SlotIndex->SlotCount SlotIndex/SlotIndex SlotIndex/SlotCount SlotIndex/Ratio SlotIndex*SlotIndex SlotIndex*SlotCount SlotIndex*Ratio 0 1 2 3 4 5 6 7 8 9 10 11 121314151617181920212223 Frame with 24 slots Affine Space In mathematics, an affine space is a geometric structure that generalizes the properties of Euclidean spaces in such a way that these are independent of the concepts of distance and measure of angles, keeping only the properties related to parallelism and ratio of lengths for parallel line segments... -- Wikipedia

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 107/119 DestClient::newCapacity(RequestId, SlotCount); TestNode::throttleCapacityTo(RequestId, SlotCount total); TEST(capacity_decrease_is_notified_to_clients) { TestNode node; DestClient client1 = node.clientWithCapacity(5); DestClient client2 = node.clientWithCapacity(8); REQUIRE_CALL(client1, newCapacity(4, 2)); REQUIRE_CALL(client2, newCapacity(4, 3)); node.throttleCapacityTo(4, 5); }

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 108/119 DestClient::newCapacity(RequestId, SlotCount); TestNode::throttleCapacityTo(RequestId, SlotCount total); TEST(capacity_decrease_is_notified_to_clients) { TestNode node; DestClient client1 = node.clientWithCapacity(5); DestClient client2 = node.clientWithCapacity(8); RequestId req{4}; REQUIRE_CALL(client1, newCapacity(req, 2)); REQUIRE_CALL(client2, newCapacity(req, 3)); node.throttleCapacityTo(req, 5); }

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 109/119 DestClient::newCapacity(RequestId, SlotCount); TestNode::throttleCapacityTo(RequestId, SlotCount total); TEST(capacity_decrease_is_notified_to_clients) { TestNode node; SlotCount c1Capacity{5}, c2Capacity{8}; DestClient client1 = node.clientWithCapacity(c1Capacity); DestClient client2 = node.clientWithCapacity(c2Capacity); RequestId req{4}; SlotCount newC1Capacity{2}, newC2Capacity{3}; REQUIRE_CALL(client1, newCapacity(req, newC1Capacity)); REQUIRE_CALL(client2, newCapacity(req, newC2Capacity)); SlotCount newTotalCapacity{5}; node.throttleCapacityTo(req, newTotalCapacity); }

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 110/119 DestClient::newCapacity(RequestId, SlotCount); TestNode::throttleCapacityTo(RequestId, SlotCount total); TEST(capacity_decrease_is_notified_to_clients) { TestNode node; SlotCount c1Capacity{5}, c2Capacity{8}; DestClient client1 = node.clientWithCapacity(c1Capacity); DestClient client2 = node.clientWithCapacity(c2Capacity); RequestId req{4}; SlotCount newC1Capacity{2}, newC2Capacity{3}; REQUIRE_CALL(client1, newCapacity(req, newC1Capacity)); REQUIRE_CALL(client2, newCapacity(req, newC2Capacity)); SlotCount newTotalCapacity{5}; node.throttleCapacityTo(req, newTotalCapacity); } WTF!

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 111/119 DestClient::newCapacity(RequestId, SlotCount); TestNode::throttleCapacityTo(RequestId, SlotCount total); TEST(capacity_decrease_is_notified_to_clients) { TestNode node; DestClient client1 = node.clientWithCapacity(SlotCount{5}); DestClient client2 = node.clientWithCapacity(SlotCount{8}); RequestId req{4}; REQUIRE_CALL(client1, newCapacity(req, SlotCount{2})); REQUIRE_CALL(client2, newCapacity(req, SlotCount{3})); node.throttleCapacityTo(req, SlotCount{5}); }

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 112/119 ● Introduction to type safety ● Type safety in C++ ● Simple library solution for strong types ● Sophisticated libraries – scouting github! ● What strong types does with your code Type Safe C++? - LOL! :-)

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 113/119 ● Safety for built in types is abysmal in C++ Type Safe C++? - LOL! :-)

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 114/119 ● Safety for built in types is abysmal in C++ ● Structs/classes are as strong as you wish – You must add the functionality you want Type Safe C++? - LOL! :-)

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 115/119 ● Safety for built in types is abysmal in C++ ● Structs/classes are as strong as you wish – You must add the functionality you want ● Libraries exist that makes this easier Type Safe C++? - LOL! :-)

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 116/119 ● Safety for built in types is abysmal in C++ ● Structs/classes are as strong as you wish – You must add the functionality you want ● Libraries exist that makes this easier ● Thinking about what operations your types should support makes you understand the problem better! – Beware of the urge for convencience! Type Safe C++? - LOL! :-)

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 117/119 ● Safety for built in types is abysmal in C++ ● Structs/classes are as strong as you wish – You must add the functionality you want ● Libraries exist that makes this easier ● Thinking about what operations your types should support makes you understand the problem better! – Beware of the urge for convencience! ● Strong types leads to more expressive code – Fewer magical numbers – More encapsulation – Explicit tests that express intent Type Safe C++? - LOL! :-)

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 118/119 ● Safety for built in types is abysmal in C++ ● Structs/classes are as strong as you wish – You must add the functionality you want ● Libraries exist that makes this easier ● Thinking about what operations your types should support makes you understand the problem better! – Beware of the urge for convencience! ● Strong types leads to more expressive code – Fewer magical numbers – More encapsulation – Explicit tests that express intent Type Safe C++? - LOL! :-) Avoid typedef

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Type Safe C++? - LOL! :-) – NDC{Techtown} 2018 – © Björn Fahller @bjorn_fahller 119/119 Björn Fahller bjorn@fahller.se @bjorn_fahller @rollbear cpplang, swedencpp Type Safe C++? - LOL! :-) https://github.com/rollbear/strong_type