Which headers in the C++ standard library are guaranteed to include another header?
Solution 1:
This answer ignores C headers - both the <meow.h> and <cmeow> ones. Of the C++ library headers (all references are to N4659):
<initializer_list> is guaranteed to be included by:
-
<utility>(§23.2.1 [utility.syn]) -
<string>(§24.3.1 [string.syn]) -
<array>(§26.3.2 [array.syn]) -
<deque>(§26.3.3 [deque.syn]) -
<forward_list>(§26.3.4 [forward_list.syn]) -
<list>(§26.3.5 [list.syn]) -
<vector>(§26.3.6 [vector.syn]) -
<map>(§26.4.2 [associative.map.syn]) -
<set>(§26.4.3 [associative.set.syn]) -
<unordered_map>(§26.5.2 [unord.map.syn]) -
<unordered_set>(§26.5.3 [unord.set.syn]) -
<queue>(§26.6.2 [queue.syn]) -
<stack>(§26.6.3 [stack.syn]) -
<algorithm>(§28.2 [algorithms.syn]) -
<random>(§29.6.2 [rand.synopsis]) -
<valarray>(§29.7.1 [valarray.syn]) -
<regex>(§31.4 [re.syn])
<iostream> is guaranteed to include <ios>, <streambuf>, <istream>, and <ostream> (§30.4.1 [iostream.syn]).
<ios> is guaranteed to include <iosfwd> (§30.5.1 [ios.syn]).
<bitset> is guaranteed to include <string> and <iosfwd> (§23.9.1 [bitset.syn]).
The free function templates std::begin, std::end, the C++14 c-, r-, and cr- versions, and the C++17 free function templates std::size, std::empty and std::data nominally reside in <iterator>, but are also available if any of the following headers is included: <array>, <deque>, <forward_list>, <list>, <map>, <regex>, <set>, <string>, <unordered_map>, <unordered_set>, and <vector> (§27.7 [iterator.range], §27.8 [iterator.container]).
When <string_view> is included, the *begin and *end functions, and the two generic std::swap overloads defined in [utility.swap] (swap(T&, T&) and swap(T (&a)[N], T (&b)[N])) are guaranteed to be available. size/empty/data, however, are not. (§24.4.1 [string.view.synop]).