Re: [boost] painless currying

Subject: Re: [boost] painless currying
From: Larry Evans (cppljevans_at_[hidden])
Date: 2011-08-24 12:29:10

On 08/23/11 14:38, Eric Niebler wrote:
> After playing around with functional languages, I've come to envy how
> easy they make it to curry functions. Call a 2-argument function with 1
> argument and you get a function that takes 1 argument. Pass another
> argument and it evaluates the function. Simple. In contrast, C++ users
> have to use binders, which are not as nice.
> 
> On a lark, I implemented a wrapper that turns any TR1-style function
> object into a "curryable" function object (attached). Successive
> function call invocations bind arguments until enough arguments are
> bound to invoke the wrapped function. With it you can do the following:
> 
>     curryable<std::plus<int> > p;
>     auto curried = p(1);
>     int i = curried(2);
>     assert(i == 3);
> 
> Is there any interest in such a thing?

Hi Eric,

I downloaded then renamed curryable.h to currable.hpp (so my emacs
editor would select c++ mode).  I also made corresponding changes in
source "curryable.h" -> "curryable.hpp".  I'm using boost 1.46 and
compiling the result gives an errors:

In file included from
/home/evansl/prog_dev/boost-svn/ro/boost_1_46_0/boost/preprocessor/iteration/detail/iter/forward2.hpp:50:0,
                 from ./curryable.hpp:157,
                 from
/home/evansl/prog_dev/boost-svn/ro/boost_1_46_0/boost/preprocessor/iteration/detail/iter/forward1.hpp:47,
                 from curryable.hpp:113,
                 from curryable.cpp:1:
./curryable.hpp:117:1: error: macro "BOOST_PP_CHECK_2" requires 2
arguments, but only 1 given
./curryable.hpp:117:1: error: macro "BOOST_PP_CHECK_2" requires 2
arguments, but only 1 given
./curryable.hpp:117:1: error: pasting ")" and "BOOST_PP_CAT" does not
give a valid preprocessing token
./curryable.hpp:175:1: error: macro "BOOST_PP_CHECK_2" requires 2
arguments, but only 1 given
./curryable.hpp:175:1: error: macro "BOOST_PP_CHECK_2" requires 2
arguments, but only 1 given
./curryable.hpp:175:1: error: pasting ")" and "BOOST_PP_CAT" does not
give a valid preprocessing token
In file included from
/home/evansl/prog_dev/boost-svn/ro/boost_1_46_0/boost/preprocessor/iteration/detail/iter/forward2.hpp:55:0,

What should I do to avoid those errors?

TIA.

-Larry