Re: [Boost-users] tuple

Subject: Re: [Boost-users] tuple
From: Noah Roberts (roberts.noah_at_[hidden])
Date: 2010-04-23 13:28:11

In article <alpine.LRH.2.00.1004221714070.12496_at_[hidden]>, 
jewillco_at_[hidden] says...
> 
> On Thu, 22 Apr 2010, luca formaggia wrote:
> 
> > Hello,
> > 
> > someone could tell me what is wrong in this piece of code
> > 
> > #include "boost/tuple/tuple.hpp"
> > using namespace boost::tuples;
> > int main(){
> >         tuple<int, double> t2();
> >         get<0>(t2)=int(10);
> > }
> > 
> > I get the following error message:
> > 
> > g++ try.cpp
> > try.cpp: In function ?int main()?:
> > try.cpp:5: error: no matching function for call to ?get(boost::tuples::tuple<int, double, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type,
> > boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type> (&)())
> > 
> > In the tutorial it is written that tuple<int, double> t2() should construct the object via the default constructor.
> 
> This syntax is not correct.  "tuple<int, double> t2();" declares a 
> function named t2 that returns a tuple<int, double>, not an actual tuple. 
> Leave off the extra parentheses to get a working version.
> 
> > Why I cannot access the first element (it works if I give an initial 
> > value, for instance using  tuple<int, double> t2(1);  I get a similar 
> > error if I use the method get<N>() instead of the function.
> 
> Adding an initial value disambiguates the statement so it is no longer a 
> function declaration.  The version of get you use does not matter to this 
> problem.

Or use initialization syntax:

typedef tuple<int,double> tuple_;
tuple_ t2 = tuple_();

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