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Why has std::swap been moved to the <utility> header for C++11?
N3290 C.2.7 says:
17.6.3.2
Effect on original feature: Function swap moved to a different header
Rationale: Remove dependency on
<algorithm>for swap.Effect on original feature: Valid C++ 2003 code that has been compiled expecting swap to be in
<algorithm>may have to instead include<utility>.
I can’t understand the part in bold. What kind of dependency is being talked about and why?
The committee wanted to allow you to use
swap()without introducing a compile-time dependency on the large and more complex<algorithm>header file. Becauseswap()is so widely used, it makes sense to let you pull in its definition with as little additional baggage as possible; this will generally lead to faster compile times for files that don’t otherwise need<algorithm>. Its new home allows it to be used without introducing unneeded overhead.