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### 3309. Is `<ios>` implicitly `#include`d by `<sstream>`, `<fstream>` etc.?

Section: 31.8 [string.streams], 31.10 [file.streams] Status: New Submitter: Jens Maurer Opened: 2019-11-01 Last modified: 2019-11-04

Priority: 3

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Discussion:

It is unclear whether the streams headers implicitly `#include <ios>` and make (for example) the name `std::basic_ios` available after including `<sstream>`.

This question becomes more important as header units arrive with modules, where there is an explicit choice whether to re-export names from subordinate headers.

[2019-11 Priority to 3 during Monday issue prioritization in Belfast]

Proposed resolution: