Re: [boost] Review Request: Dataflow.Signals

From: Christian Henning (chhenning_at_[hidden])
Date: 2008-03-11 22:45:00

Stjepan, quick update. I have fixed an error on my side using MSVC 7.1.

I copied now all code from the first example and get the following
compiler errors:

c:\Code Samples\boost\dataflow\first\first.cpp(71) : error C2893:
Failed to specialize function template
'boost::enable_if<boost::mpl::and_<boost::dataflow::has_default_port<OutgoingPort,boost::dataflow::args::left,boost::dataflow::signals::connect_mechanism,boost::dataflow::signals::tag>,boost::dataflow::has_default_port<IncomingPort,boost::dataflow::args::right,boost::dataflow::signals::connect_mechanism,boost::dataflow::signals::tag>>,OutgoingPort&>::type
boost::signals::operator >>=(OutgoingPort &,const IncomingPort &)'
        With the following template arguments:
        'processor'
        'output'
c:\Code Samples\boost\dataflow\first\first.cpp(71) : error C2893:
Failed to specialize function template
'boost::enable_if<boost::mpl::and_<boost::dataflow::has_default_port<OutgoingPort,boost::dataflow::args::left,boost::dataflow::signals::connect_mechanism,boost::dataflow::signals::tag>,boost::dataflow::has_default_port<IncomingPort,boost::dataflow::args::right,boost::dataflow::signals::connect_mechanism,boost::dataflow::signals::tag>>,OutgoingPort&>::type
boost::signals::operator >>=(OutgoingPort &,IncomingPort &)'
        With the following template arguments:
        'processor'
        'output'
c:\Code Samples\boost\dataflow\first\first.cpp(71) : error C2676:
binary '>>=' : 'processor' does not define this operator or a
conversion to a type acceptable to the predefined operator

Weird, I can compile more with 7.1 than with 8. Below is my code.

Christian

#include <iostream>
#include <tchar.h>

#include <boost/dataflow/signals/component/filter.hpp>
#include <boost/dataflow/signals/component/storage.hpp>
#include <boost/dataflow/signals/component/timed_generator.hpp>
#include <boost/dataflow/signals/connection.hpp>

#include <boost/random/mersenne_twister.hpp>
#include <boost/random/normal_distribution.hpp>
#include <boost/random/variate_generator.hpp>

using namespace boost;

class processor : public signals::filter<processor, void (double)>
{
public:
    // Initialize the Gaussian noise generator.
    processor() : generator(mt, dist) {}

    // Receive void(double) signals, add some Gaussian noise, and send
    // out the modified value.
    void operator()(double x)
    {
        out(x + generator());
    }
private:
    mt19937 mt;
    normal_distribution<> dist;
    boost::variate_generator<mt19937&, boost::normal_distribution<> > generator;
};

// This will be our data output.  We just need to make a function object,
// and specify that it is a signals::call_consumer.
class output
{
public:
    typedef dataflow::signals::call_consumer<>  dataflow_traits;

    void operator()(double x)
    {
        std::cout << x << std::endl;
    }
};

int _tmain(int argc, _TCHAR* argv[])
{
    // For our data source, we will use timed_generator,
    // which creates its own thread and outputs it's stored value
    // at a specified time interval.  We'll store a value of 0 to be sent out.
    // The signature void(double) specifies that the signal carries a double,
    // and that there is no return value.
    signals::timed_generator<void (double)> input(0);

    // Data processor and output:
    processor proc;
    output out;

    // ---Connect the dataflow network ---------------------
    //
    //     ,---------.     ,---------.     ,---------.
    //     |  input  | --> |  proc   | --> |   out   |
    //     `---------'     `---------'     `---------'
    //
    // -----------------------------------------------------
    input >>= proc >>= out;

    // If you prefer, you can also do:
    // connect(input, proc);
    // connect(proc, out);

    // Tell the source to start producing data, every 0.5s:
    input.enable(0.5);

    // take a little nap :-)
    boost::xtime xt;
    boost::xtime_get(&xt, boost::TIME_UTC);
    xt.sec += 10;
    boost::thread::sleep(xt);

    input.join();
    return 0;
}