On 09/03/11 08:28, Larry Evans wrote:
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: [snip] With the revised curryable.cpp, 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 test<1>: type_u<0>() type_u<0,1>(type_u const&) type_u<0,1>(type_u const&) type_u<1>() type_u<1,1>(type_u const&) type_u<0,1>(type_u const&) type_u<0,1>(type_u const&) type_u<1,1>(type_u const&) type_u<2>() sout<<type_u<0> sout<<type_u<1> sout<<type_u<2> test<0>: type_u<0>() type_u<0,0>(type_u const&) type_u<0,0>(type_u const&) type_u<1>() type_u<1,0>(type_u const&) type_u<0,0>(type_u const&) type_u<0,0>(type_u const&) type_u<1,0>(type_u const&) type_u<2>() type_u<2,0>(type_u const&) type_u<0,0>(type_u const&) type_u<1,0>(type_u const&) type_u<0,0>(type_u const&) type_u<1,0>(type_u const&) type_u<2,0>(type_u const&) type_u<3>() type_u<3,0>(type_u const&) type_u<0,0>(type_u const&) type_u<1,0>(type_u const&) type_u<2,0>(type_u const&) type_u<0,0>(type_u const&) type_u<1,0>(type_u const&) type_u<2,0>(type_u const&) type_u<3,0>(type_u const&) type_u<4>() type_u<4,0>(type_u const&) type_u<0,0>(type_u const&) type_u<1,0>(type_u const&) type_u<2,0>(type_u const&) type_u<3,0>(type_u const&) type_u<0,0>(type_u const&) type_u<1,0>(type_u const&) type_u<2,0>(type_u const&) type_u<3,0>(type_u const&) type_u<4,0>(type_u const&) type_u<5>() type_u<5,0>(type_u const&) type_u<0,0>(type_u const&) type_u<1,0>(type_u const&) type_u<2,0>(type_u const&) type_u<3,0>(type_u const&) type_u<4,0>(type_u const&) type_u<0,0>(type_u const&) type_u<1,0>(type_u const&) type_u<2,0>(type_u const&) type_u<3,0>(type_u const&) type_u<4,0>(type_u const&) type_u<5,0>(type_u const&) Compilation finished at Sat Sep 3 09:41:23 which reveals that, when passed arguments that cannot possibly be valid, the arguments just keep accummulating in the curryable<F,Args...>::argI. It would be helpful if some diagnostic were issued in case too many arguments are supplied. -regards, Larry