How to remove boilerplate in vector of tuple initialization?

Question

I'd like to initialize a list of 5-tuples of strings like this:

std::vector<std::tuple<std::string,std::string,std::string,std::string,std::string> >
    examples = 
  {
    {"/foo"                 ,"/"           ,"foo"        ,""   ,"foo"},
    {"/foo/"                ,"/"           ,"foo"        ,""   ,"foo"},
    {"/foo//"               ,"/"           ,"foo"        ,""   ,"foo"},
    {"/foo/./"              ,"/foo"        ,"."          ,""   ,""},
    {"/foo/bar"             ,"/foo"        ,"bar"        ,""   ,"bar"},
    {"/foo/bar."            ,"/foo"        ,"bar."       ,""   ,"bar"},
    {"/foo/bar.txt"         ,"/foo"        ,"bar.txt"    ,"txt","bar"},
    {"/foo/bar.txt.zip"     ,"/foo"        ,"bar.txt.zip","zip","bar.txt"},
    {"/foo/bar.dir/"        ,"/foo"        ,"bar.dir"    ,"dir","bar"},
    {"/foo/bar.dir/file"    ,"/foo/bar.dir","file"       ,""   ,"file"},
    {"/foo/bar.dir/file.txt","/foo/bar.dir","file.txt"   ,"txt","file"}
  };

This question asks why nested initializer lists can't be used for vector of tuples: the answers say to use std::make_tuple. But this makes my code look ridiculous:

std::vector<std::tuple<std::string,std::string,std::string,std::string,std::string> >
    examples = 
  {
    std::make_tuple<std::string,std::string,std::string,std::string,std::string>("/foo"                 ,"/"           ,"foo"        ,""   ,"foo"),
    std::make_tuple<std::string,std::string,std::string,std::string,std::string>("/foo/"                ,"/"           ,"foo"        ,""   ,"foo"),
    std::make_tuple<std::string,std::string,std::string,std::string,std::string>("/foo//"               ,"/"           ,"foo"        ,""   ,"foo"),
    std::make_tuple<std::string,std::string,std::string,std::string,std::string>("/foo/./"              ,"/foo"        ,"."          ,""   ,""),
    std::make_tuple<std::string,std::string,std::string,std::string,std::string>("/foo/bar"             ,"/foo"        ,"bar"        ,""   ,"bar"),
    std::make_tuple<std::string,std::string,std::string,std::string,std::string>("/foo/bar."            ,"/foo"        ,"bar."       ,""   ,"bar"),
    std::make_tuple<std::string,std::string,std::string,std::string,std::string>("/foo/bar.txt"         ,"/foo"        ,"bar.txt"    ,"txt","bar"),
    std::make_tuple<std::string,std::string,std::string,std::string,std::string>("/foo/bar.txt.zip"     ,"/foo"        ,"bar.txt.zip","zip","bar.txt"),
    std::make_tuple<std::string,std::string,std::string,std::string,std::string>("/foo/bar.dir/"        ,"/foo"        ,"bar.dir"    ,"dir","bar"),
    std::make_tuple<std::string,std::string,std::string,std::string,std::string>("/foo/bar.dir/file"    ,"/foo/bar.dir","file"       ,""   ,"file"),
    std::make_tuple<std::string,std::string,std::string,std::string,std::string>("/foo/bar.dir/file.txt","/foo/bar.dir","file.txt"   ,"txt","file")
  };

If I can't get rid of the std::make_tuple<...>, can I at least use typedef or using to remove the clutter in the code?

using StringQuintet = std::tuple<std::string,std::string,std::string,std::string,std::string>; doesn't help because std::make_tuple<...> needs just the tuples template arguments not the tuple type.

Is there a good way to clean up this boilerplate looking mess?

Using explicit template arguments in std::make_tuple defeats its purpose. Just use std::tuple directly. — tkausl
– tkausl, Commented Sep 26, 2018 at 2:57
the point of make_tuple is to deduce types from the initializers, so you don't have to specify the type list — M.M
– M.M, Commented Sep 26, 2018 at 2:58
std::make_tuple() is a function it will deduce the types so you don't need to explicitly mention them. Though you will need to use the std::string literal rather than the C-String literal. — Loki Astari
– Loki Astari, Commented Sep 26, 2018 at 3:03

Yakk - Adam Nevraumont · Accepted Answer · 2018-09-26 03:06:08Z

3

 std::make_tuple<std::string,std::string,std::string,std::string,std::string>("/foo"                 ,"/"           ,"foo"        ,""   ,"foo"),

you don't pass types to make tuple.

std::make_tuple("/foo"                 ,"/"           ,"foo"        ,""   ,"foo"),

you let the compiler deduce them. Alternatively:

std::make_tuple("/foo"s                 ,"/"s           ,"foo"s        ,""s   ,"foo"s),

to have std string literals (using namespace std::literals; to permit this).

Or:

using StringQuintet = std::tuple<std::string,std::string,std::string,std::string,std::string>;
// ...
StringQuintet("/foo"                 ,"/"           ,"foo"        ,""   ,"foo"),

answered Sep 26, 2018 at 3:06

Yakk - Adam Nevraumont

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Loki Astari · Accepted Answer · 2018-09-26 03:05:47Z

0

Use std::make_tuple:

using namespace std::string_literals;
....

std::make_tuple("/foo"s                 ,"/"s           ,"foo"s        ,""s   ,"foo"s),

....

answered Sep 26, 2018 at 3:05

Loki Astari

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