[Boost-users] [Proto] EvalStream Revisited -- Segmentation Fault

Subject: [Boost-users] [Proto] EvalStream Revisited -- Segmentation Fault
From: Hossein Haeri (powerprogman_at_[hidden])
Date: 2011-01-03 19:37:53

Dear all,

A few weeks ago, I asked for help about an EDSL which can handle expressions like

x >> f >> g >> h

so that they're equivalent to h(g(f(x))) once evaluated. Eric kindly provided me with the solution in the P.S.

I was just playing around with his code and thought about extending it with a simple case when f's and g's are actually functions, as opposed to function objects. So, I added the following two lines:

int plus1(int i) {return i + 1;}

const terminal<pointer_to_unary_function<int, int> >::type plus_one = {ptr_fun(&plus1)};

And, I get a segmentation fault (GCC 4.5.1, MinGW32, WinXP, SP3) when I run the following line:

1 >> plus_one >> plus_one

Any ideas?

TIA,
--Hossein

P.S.

  #include <boost/proto/proto.hpp>
  #include <iostream>
  namespace proto = boost::proto;
  using proto::_;

  struct add_one_ {
    typedef int result_type;
    int operator()(int i) const {
      return i + 1;
    }
  };

  proto::terminal<add_one_>::type const add_one = {};

  struct GetFun
    : proto::call<proto::_value(proto::_right)>
  {};

  struct EvalStream
    : proto::or_<
          proto::when<
              proto::terminal<_>
            , proto::_value
          >
        , proto::when<
              proto::shift_right<EvalStream, proto::terminal<_> >
            , proto::lazy< GetFun(EvalStream(proto::_left)) >
          >
      >
  {};

  int main()
  {
      // This prints "3"
      std::cout << EvalStream()( 1 >> add_one >> add_one ) << std::endl;
  }