[Boost-users] hash<pair<...

Subject: [Boost-users] hash<pair<...
From: John Dlugosz (JDlugosz_at_[hidden])
Date: 2009-09-17 17:21:14

I just moved a project that was using VC8, with TR1 supplied via BOOST, to VC9 with its own TR1 implementation.

I was surprised that a unordered_map failed to compile with a great deal of verboseness because it didn't like my key type.  I used a pair of two primitive types as the key.  Boost took that just fine.

But looking at the current Boost documentation for the hash object, (<http://www.boost.org/doc/libs/1_40_0/doc/html/boost_tr1/subject_list.html#boost_tr1.subject_list.hash>) I see that the hash specializations include primitive types, strings, but not tuples.

Is this something that changed between Boost 1_38 and 1_40, or an undocumented extension, or what?  Why would the standard leave out that, when everyone and his neighbor will just supply their own generic definition.  That is, is there a good reason for not doing it?

--John

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