dry-comparisons

This is the source code for the any_of, all_of and none_of C++17 utility mentioned in the blog post "DRY multicomparisons"

Public domain.

Usage

using rollbear::any_of;

class Machine
{
public:
  ...
  void func() {
    assert(state == any_of(S1, S3)); // assert(state == S1 || state == S3);
    ...
  }
private:
  enum { S0, S1, S2, S3 } state;
};

The types available are any_of, all_of and none_of.

iff all member types can be inserted into an ostream, an instance of any_of, all_of or none_of may be printed, e.g. std::cout << rollbear::any_of{1,3,5}, which will produce the output any_of{1,3,5}.

iff it is possible to do logical and/or operations on all members, instances of any_of, all_of and none_of may be used directly as boolean expressions.

• bool(any_of{a,b,c}) == bool(a || b || c)
• bool(all_of{a,b,c}) == bool(a && b && c)
• bool(none_of{a,b,c}) == !bool(a || b || c)

iff the members are callable, the resulting object is also callable.

• any_of{std::plus{}, std::minus{}}(3,2) == 5
• all_of{std::plus{}, std::minus{}}(3,2) > 0
• none_of{std::plus{}, std::minus{}}(3,2) == 0

with SFINAE friendly checks that the calls can be made for the values given. The logical conditions are short cirquited, in the normal logical expression manners.

Further more, it is also possible to do relational comparisons. For example:

assert(all_of(s1, s2) > "."), providing the expressions s1 and s2 are greater-than comparable with a string literal.