On Fri, Jun 5, 2015 at 8:21 AM, Uthpal Urubail wrote:

Experts,

I am using boost::tuple as key in std::map. I would like to write my own comparison method (considering tolerance in comparison)

What's the question?

The default comparison defined in tuple_comparison.hpp is of no use to me.

Seems like this is less of a boost question and more of a general C++ question. std::map, or any range, comparisons, generally take a const & of whatever the type is, key, item, whatever, and may return bool, int (or other integral type), etc. How you actually implement it is up to you. Could be a function, functor, lambda expression, whatever, AFAIK.

Any help in this is highly appreciated.

HTH

Regards,

UJ

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On 5 Jun 2015, at 13:21, Uthpal Urubail wrote:

Experts, I am using boost::tuple as key in std::map. I would like to write my own comparison method (considering tolerance in comparison)

Map comparators must impose a strict weak ordering on the keys. Typically trying to use a tolerance means that transitivity is violated (ie a <= b and b <= c does not imply a <= c). If you must use floating point types as keys you need to be careful.