while browsing one of my old questions on constexpr I stumbled onto a very(IMHO) important comment. Basically it boils down to : (this is legal C++11 :( )

 constexpr double f(bool b)
 {
 return b? 42:42/(rand()+1); // how pure is rand ;)
 }

My question is what is the reason this is allowed by the standard. Since Im a big fan of referential transparency I hope they have a good reason :) and I would like to know it.

BTW there is related Q but most of the A even dont mention pure thing, or when they do they dont specify the reasoning why std allows this. Relation between constexpr and pure functions

c++ c++11 constexpr
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