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?
With the 2 attached files (compiled with gcc4.6 and with boost trunk [which svn update showed was revision 74198]), the output is: /home/evansl/prog_dev/boost-svn/ro/trunk/sandbox-local/build/gcc4_6v/boost-svn/ro/trunk/sandbox/rw/variadic_templates/sandbox/painless_currying/curryable.exe type_u<0>() type_u<0>(type_u const&) type_u<0>(type_u const&) type_u<1>() type_u<1>(type_u const&) type_u<0>(type_u const&) type_u<0>(type_u const&) type_u<1>(type_u const&) type_u<2>() sout<<type_u<0> sout<<type_u<1> sout<<type_u<2> Compilation finished at Sat Sep 3 08:20:45 which shows several copy CTOR's executed. These copy CTOR calls were caused by the code like this: curryable (Fun f, Arg0 a0, Arg1 a1, Arg2 a2): fun (f), arg0 (a0), arg1 (a1), arg2 (a2) { } produced by the BOOST_PP code. Is there any way to prevent these copies, maybe by declarations like: Arg0 const& arg0; instead of the existing: Arg0 arg0; ? -regards, Larry