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eac6afacdc
Also added a C++14 configuration to testing, but using it only for bidrectional map testing at the moment.
74 lines
2.5 KiB
C++
74 lines
2.5 KiB
C++
// This file was generated automatically.
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// Scope and safety
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//
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// This tutorial shows some of the safety features of Better Enums: scope, how
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// to control conversions, and the lack of a default constructor.
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//
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// Scope
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//
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// You have probably noticed by now that Better Enums are scoped: when you
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// declare
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#include <cassert>
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#include <enum.h>
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ENUM(Channel, int, Red = 1, Green, Blue)
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// you don't get names such as Red in the global namespace. Instead, you get
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// Channel, and Red is accessible as Channel::Red. This is no big deal in C++11,
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// which has enum class. In C++98, however, this typically requires effort.
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// Better Enums brings scope uniformly to both variants. So, despite the above
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// declaration, you can safely declare
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ENUM(Node, char, Red, Black)
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// and everything will work as expected.
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int main()
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{
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assert((+Channel::Red)._to_integral() != (+Node::Red)._to_integral());
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// Implicit conversion
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//
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// A major complaint in C++98 is that enums are implicitly convertible to
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// integers. Unfortunately, that is also true of Better Enums, and I haven't
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// found a way to forbid the conversions and still have switch case checking.
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//
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// Better Enums can be made as safe as enum class in C++11, however. If your
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// compiler supports enum class and you define BETTER_ENUMS_STRICT_CONVERSION
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// before including enum.h, the following code will not compile:
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//
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// Channel channel = Channel::Red;
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// int n = channel;
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//
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// The reason this is not enabled by default is explained in the reference page
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// on strict conversions.
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//
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// Default constructor
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//
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// Better Enums don't have a default constructor, for three reasons.
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//
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// 1. Better Enums is a library that can't know what your application would
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// like the default value to be for each enum, or whether you even want
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// one.
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// 2. I chose not to leave the default value undefined, because the idea is to
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// encourage the convention that whenever a Better Enum exists, it has a
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// valid value. This is borrowed from typed functional programming.
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// 3. Better Enums is still under development, and this option is the most
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// future-proof.
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//
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// So, if you uncomment this code, the file won't compile:
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//
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// Channel channel;
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//
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// This may be too strict, and I may relax it in the future. In the meantime,
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// the solution sketched in the special values demo can replace default
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// constructors for some purposes, and in a more flexible way. I may eventually
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// have the default constructor calling a template function like the one in that
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// demo.
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return 0;
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}
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