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Re: unordered_map with valarray as key

From: David Fang <fang at csl dot cornell dot edu>
To: Daniel Krügler <daniel dot kruegler at gmail dot com>
Cc: Daniel Molina García <unomas at correo dot ugr dot es>, libstdc++ <libstdc++ at gcc dot gnu dot org>
Date: Mon, 28 Oct 2013 19:18:53 -0400 (EDT)
Subject: Re: unordered_map with valarray as key
Authentication-results: sourceware.org; auth=none
References: <1382964043 dot 2909 dot 10 dot camel at do-what-u-should> <CAGNvRgALW8Wt-xfEb48Pj7GFKoiewAcz=3q4wPTq3dCpDr0fww at mail dot gmail dot com>

2013/10/28 Daniel Molina García <unomas@correo.ugr.es>:

I'm not sure if my code is valid, but I think that unordered_map is not
working ok with valarray as key.


Correct. The code is invalid, because the standard does not specify a
specialization of std::hash for std::valarray.

- Daniel

However, nothing stops one from providing a specialization ofstd::hash<std::valarray<> >. You could look at hash<std::string> rohash<const char*> as a starting point.


Fang

Follow-Ups:
- Re: unordered_map with valarray as key
  - From: Jonathan Wakely

References:
- unordered_map with valarray as key
  - From: Daniel Molina García
- Re: unordered_map with valarray as key
  - From: Daniel Krügler

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