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std::vector as key in std::map?

Started by Calexus Jul 6, 2011 at 12:49 PM 2 replies 1.5k views

Original Post

Jul 6, 2011 at 12:49 PM

I'm in the process of debugging a rather massive system and I keep getting back to a part of the code that makes heavy use of std::map, std::long >, the code itself compiles perfectly well and for what I hear it has been working fine for years.

But still... is it really legal to use an std::vector as a key? I have never seen anyone use it before but I guess its legal as long as all the needed operators are provided.

Edit >> Sry forgot to say this is C++.

alvaro

Jul 6, 2011 at 12:53 PM

You have to make sure you provide an operator< that is a strict weak ordering. The lexicographical order, for instance, should work.

Antheus

Jul 6, 2011 at 12:59 PM

Edit >> Sry forgot to say this is C++.

Technically, this is madness.

SiCrane

Jul 6, 2011 at 1:35 PM

You have to make sure you provide an operator< that is a strict weak ordering. The lexicographical order, for instance, should work.

All standard library containers provide operator< by default that is implemented in terms of std::lexicographical_compare(). You don't need to supply it yourself.

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