Re: [boost] [Foreach] Proposal to simplify using Boost.Foreach withmaps

Subject: Re: [boost] [Foreach] Proposal to simplify using Boost.Foreach withmaps
From: Christian Schladetsch (christian.schladetsch_at_[hidden])
Date: 2009-09-14 19:07:19

Compare:

// (1) my typical use, where Map is a typedef or a template parameter
foreach (Map::reference val, map)
{
   action(val.first, val.second);
}

// (2) use based on typedef'd container
foreach_pair (Map::key_type const &key, Map::referent_type &val, map)
{
    action(key, val);
}

// (3) use references
foreach_pair (Key const &key, Value &val, map)
{
    action(key, val);
}

// (4) copying without a typedef
foreach_pair (Key key, Val val, map)
{
    action(key, val);
}

A hidden cost of (3) and (4) is the extra work required when refactoring.

On Tue, Sep 15, 2009 at 10:22 AM, Pete Bartlett <pete_at_[hidden]> wrote:

> Christian Schladetsch wrote:
> >Is there any performance difference between
> >
> >BOOST_FOREACH_PAIR(K const &key, V &val, map)
> >{
> >}
> >
> >and
> >
> >BOOST_FOREACH(Map::reference ref, map)
> >{
> >}
>
> I haven't tested this specific case but in previous discussions and tests
> on
> this subject, I found these extra for-loops of fixed "length" 1 hidden in
> the macro expansion were optimized well by popular compilers, so the hit
> may
> be negligible.
>
> Pete
>
>
>
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