boost variant comparator

Question

I need to compare two variables of type boost::variant and I want to compare the values inside the variant for equality.

What would be the best way to implement this?

My variant looks like this:

typedef boost::variant<int, float, double, long, bool, std::string, boost::posix_time::ptime> variant;

Are you sure you *really* need this variant? – Yakov Galka Jan 03 '11 at 14:14 — Yakov Galka, Jan 03 '11 at 14:14
Yes I do need this variant... – Tony The Lion Jan 03 '11 at 14:19 — Tony The Lion, Jan 03 '11 at 14:19

score 11 · Accepted Answer · answered Jan 03 '11 at 14:19

11

From variant docs:

EqualityComparable: variant is itself EqualityComparable if and only if every one of its bounded types meets the requirements of the concept.

So variant already implements equality if all the types are comparable. So in your case you should be able to just use the operator ==.

In general, you can implement a binary visitor by creating a unary visitor that encloses a reference to one of the arguments and applying the visitor to the second argument.

answered Jan 03 '11 at 14:19

Giuseppe Ottaviano

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Though this is not a real problem, with boost 1.45 and VC100 "==" works but "!=" works not an gives a compiler error (" no operator found ..."). – Semjon Mössinger Jan 11 '17 at 10:39

boost variant comparator

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