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[mrpt-typemeta]

Detailed Description

Metaprogramming header-only library to obtain constexpr textual string representations of enum types and type names, including smart pointers and complex STL compound types.

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Library mrpt-typemeta

[New in MRPT 2.0.0]

This library is part of MRPT but has no dependencies, so it can be installed in Debian-based systems with:

    sudo apt install libmrpt-typemeta-dev

Example #1: compile-time type/struct/class names to strings

Use mrpt::typemeta::TTypeName to extract a constexpr string with a compiler-independent representation of arbitrarily-complex types and STL containers. Note that creating objects from a run-time string representation of its type is handled in a different library ([mrpt-serialization]).

See: typemeta_TTypeName/test.cpp

#include <iostream>
#include <memory> // shared_ptr
// Declare custom user types:
struct MyFooClass
{
};
namespace MyNS
{
struct MyBarClass
{
};
struct MyBarClass2
{
};
}
{
using namespace std;
using namespace mrpt::typemeta;
// Evaluation of type names as constexpr strings:
constexpr auto s1 = TTypeName<int32_t>::get();
cout << s1 << endl;
cout << TTypeName<set<vector<double>>>::get() << endl;
// Evaluation of user-defined types:
cout << TTypeName<MyFooClass>::get() << endl;
cout << TTypeName<MyFooClass::Ptr>::get() << endl;
cout << TTypeName<MyNS::MyBarClass>::get() << endl;
cout << TTypeName<MyNS::MyBarClass2>::get() << endl;
// STL typenames as strings:
cout << TTypeName<double>::get() << endl;
cout << TTypeName<vector<double>>::get() << endl;
cout << TTypeName<array<int32_t, 5>>::get() << endl;
cout << TTypeName<set<double>>::get() << endl;
cout << TTypeName<pair<int32_t, pair<int32_t, int32_t>>>::get() << endl;
cout << TTypeName<map<double, set<int32_t>>>::get() << endl;
cout << TTypeName<set<
multimap<double, pair<MyFooClass, MyNS::MyBarClass2>>>>::get()
<< endl;
}

Output:

int32_t
std::set<std::vector<double>>
MyFooClass
std::shared_ptr<MyFooClass>
MyNS::MyBarClass
MyNS::MyBarClass2
double
std::vector<double>
std::array<int32_t,5>
std::set<double>
std::pair<int32_t,std::pair<int32_t,int32_t>>
std::map<double,std::set<int32_t>>
std::set<std::multimap<double,std::pair<MyFooClass,MyNS::MyBarClass2>>>

Example #2: compile-time constexpr strings manipulation

See: typemeta_StaticString/test.cpp

#include <iostream>
{
using namespace std;
using namespace mrpt::typemeta;
constexpr string_literal<3> s = "foo";
cout << "string_literal<3>=" << s << endl;
constexpr auto a = literal("foo");
constexpr auto b = literal("bar");
// In GCC7 this can be "constexpr", but it fails in MSVC 2017 (!)
auto ab = a + b;
cout << "a=" << a << endl;
cout << "b=" << b << endl;
cout << "a+b=" << ab << endl;
static_assert(ab.size() == 6, "***");
cout << "(a+b).size()=" << ab.size() << endl;
cout << "(a+b)[0]=" << ab[0] << endl;
cout << "(a+b)[5]=" << ab[5] << endl;
}

Output:

string_literal<3>=foo
a=foo
b=bar
a+b=foobar
(a+b).size()=6
(a+b)[0]=f
(a+b)[5]=r

Example #3: compile-time numbers to strings

See: typemeta_StaticString/test.cpp

#include <iostream>
{
using namespace std;
using namespace mrpt::typemeta;
constexpr auto n42 = num_to_string<42>::value;
constexpr auto n9999 = num_to_string<9999>::value;
cout << "42 as string=" << n42 << endl;
cout << "9999 as string=" << n9999 << endl;
}

Output:

42 as string=42
9999 as string=9999

Example #4: enum values to/from strings

See: typemeta_TEnumType/test.cpp

#include <iostream>
#include <string>
// Example declaration of "enum class"
enum class TestColors
{
Black = 0,
Gray = 7,
White = 15
};
// Example declaration of plain enum
{
};
// Example declaration of "enum class"
{
using namespace std;
using namespace mrpt::typemeta;
cout << "White => " << (int)TEnumType<TestColors>::name2value("White")
<< endl;
cout << "Black => " << (int)TEnumType<TestColors>::name2value("Black")
<< endl;
cout << "Gray => " << (int)TEnumType<TestColors>::name2value("Gray")
<< endl;
<< endl;
}

Output:

White => 15
Black => 0
Gray => 7
7 <= Gray

Classes

struct  mrpt::typemeta::TTypeName< T >
 A template to obtain the type of its argument as a string at compile time. More...
 



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