Templated header-only library for lexicographically comparing objects.
Tired of writing your own less-than operators for classes? Wish you could use something like std::lexicographical_compare to automatically generate it?
Now that C++ has variadic templates you can! Just include this header-only library and specify which fields, methods or custom functions you want your classes to be compared with!
- Member variables. usage: &Class::var. result: lhs.var < rhs.var
- Member methods. usage: &Class::method. result: lhs.method() < rhs.method()
- Custom functions. usage: f. result: f(lhs) < f(rhs)
- Custom predicates. usage: LCOPRED(Class, f). result: f(lhs, rhs)
Example:
struct Dog
{
int getBones() const;
int toyCount() const;
int age;
};
bool customPredicate(const Dog& lhs, const Dog& rhs);
bool operator<(const Dog& lhs, const Dog& rhs)
{
return lco::LessThan(
lhs,
rhs,
&Dog::age, // member variable
&Dog::getBones, // member method
[](const Dog& d) -> int {
return d.toyCount(); // custom function
},
LCOPRED(Dog, customPredicate) // custom predicate
);
}or to create a functor:
auto comp = lco::Functor<Dog>::make(&Dog::age, &Dog::getBones, &someFunction);
// call it
comp(dog1, dog2);
// or pass it to STL containers/etc
std::map<std::string, Dog, decltype(comp)> dogs(comp);Functors can compare by-reference or by-pointer
Working examples are shown in test.cpp
Include just lex_compare.hpp for calling less-than or lex_compare_functor.hpp (which needs lex_compare.hpp) if you need the comparison in functor form, or you could just use std::bind on it I guess.