Re: [Boost-users] [Bind] Understanding protect

On 03/28/2012 11:45 AM, Robert Jones wrote:

On Wed, Mar 28, 2012 at 10:04 AM, Thomas Heller wrote:

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On 03/28/2012 09:47 AM, Robert Jones wrote:

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On Tue, Mar 27, 2012 at 8:24 PM, Thomas Heller **wrote:

You might also want to consider phoenix::lambda, it is like protect, but

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slightly more powerful. your example would then read: #include

int main( ) { std::vector<int> v; v += 0,1,2,3,4,5,6; using boost::phoenix::bind; using boost::phoenix::lambda; using boost::phoenix::placeholders::****_1; using boost::phoenix::local_names::_****1;

for_each( v.begin( ), v.end( ), bind(g, lambda(_a = _1)[bind(f, _a)]));

return 0; }

Please don't remind me! I'd love to, but I'm stuck in the antediluvian days of 1.37!

- Rob.

Ouch. In that case, protect should work just fine. Here is a complete and working example: https://gist.github.com/**2224915https://gist.github.com/2224915

Hi Tom

Thanks for the time you've spent on this- much appreciated.

I can see where you're going with this approach, however if I've understood it correctly it sidesteps the hard bit in that the function g() now takes a unary callable and a value. My key constraint here is that g() MUST take a nullary callable object, and hence the bind machinations MUST produce a fully bound, unevaluated, nullary callable object.

I feel like I'm banging-on a bit here - sorry! Ha, no problem, I enjoy solving such problems :) After jumping through all kinds of different hoops, I updated the gist: https://gist.github.com/2224918

I hope this fits your usecase better :) The original function is unchanged, I just added the trampoline to rebind the bound functor. Well, not the most elegant solution, but might work.

Thx, Rob.

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Note that I had to get rid of the template. free template functions are a pain to bind, you would need to somehow cast it to the correct function type, which is unnecessarily clutter, and gets worse in your case. I suggest using functors, there, templates are not a problem at all: <https://gist.github.com/**2224920https://gist.github.com/2224920> < https://gist.github.com/**2224920https://gist.github.com/2224920> https://gist.github.**com/2224918https://gist.github.com/2224918 To sketch the full picture, phoenix is able to handle that in a saner fashion (sorry for the plug, take it as future reference, I don't want to make your life miserable): https://gist.github.com/**2224920https://gist.github.com/2224920 Note that in the phoenix solution, bind is not necessary anymore. Phoenix is able to adapt (even templated) functions to know how to lazily evaluate them.

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