And my question is, am I allowed to implement the competency test of static_map in g++-7? I have just implemented my own version of static_map which supports the following operations:

constexpr StaticMap<int, const char *, 3> m(make_pair(2, "abc"), make_pair(4, "def"), make_pair(6, "ghi"));

if (!m[4]) abort(); const char *foo = m[2]; return 0;

Note the compiler will elide m[2] in any case because you do nothing with its result. Therefore the compiler can assume the call does nothing and remove it.

So I was wondering did I pass the test?

Maybe. You should be aware that other students have submitted some really good implementations already, ones which work perfectly on both GCC and clang and have a STL idiomatic API and have O(1) compile time complexity and O(N) storage overheads. I have yet to see a student submit a working implementation for Visual Studio however (VS2017 finally has full constexpr, it should be doable). Also remember that the mapped values by static_map are *mutable* even though the map itself is all compile-time. And the mutability should be compiled into minimum assembler e.g.: m[2] = 5; turns into: lea addr_of_map, %eax; movl #5, [%eax, #someoffset]; ... or something similarly minimum. Feel free to email me privately with a link to your implementation for a quick review. Niall -- ned Productions Limited Consulting http://www.nedproductions.biz/ http://ie.linkedin.com/in/nialldouglas/

Hi, I would like to share my progress on the competency project made recently. I managed to implement: constexpr std::pair<const int, const char *> map_data[] = { { 5, "apple" }, { 8, "pear" }, { 0, "banana" } }; constexpr auto cmap = make_static_map(map_data); if (!has_str(cmap, "apple")) abort(); if (!has_str(cmap, "pear")) abort(); if(!cmap[8]) abort(); const char *foo=cmap[5]; const char *bar = std::get<2>(cmap); if (strcmp(bar, "banana")) abort(); // system(cmap[8]); auto m = make_static_map(map_data); m[0] = "strawberry"; system(m[0]); with zero runtime overhead and O(1) compile-time complexity(measured by template instantiation) on g++-6+ and clang-3.6+ with flag -std=c++14 and -O3. It is also experimented that zero runtime and O(1) compile-time complexity could be achieved on constant path of g++-5. In the next few days, I'm going to focus on MSVC2017 efficient implementation. Regarding the design of static_map's interface, I doubt that is it possible or worthwhile to implement a subscript-like operator/function that checks boundary at compile time(given that key is a constant expression)? Compilation errors tend to be more likely to be discovered than runtime exception. Thanks, On 03/04/2017 12:18 AM, Vic Luo wrote:

Hi,

I'm Zheng Luo, a third-year undergraduate from Shanghai Jiaotong University who have special interest in C++ programming(especially for templates). This is my second year of applying Google Summer of Code and I'm willing to contribute to Static Map project mentioned on SoC2017 page. Previously I worked for a company as a C++ intern for months on Chromium-related projects where I gained some experience about C++ in industry.

And my question is, am I allowed to implement the competency test of static_map in g++-7? I have just implemented my own version of static_map which supports the following operations:

constexpr StaticMap<int, const char *, 3> m(make_pair(2, "abc"), make_pair(4, "def"), make_pair(6, "ghi"));

if (!m[4]) abort(); const char *foo = m[2]; return 0;

which is compiled into assembly as:

main: xorl %eax, %eax ret

under g++-7 with -std=c++1z -O3

So I was wondering did I pass the test?

Thanks,

-- --------------------------------- Vic Luo Shanghai Jiaotong University Key fingerprint 0x98809ca08bf5662a