Re: [Boost-users] [proto] : Recursive functions in a lambda like language

xpressive's tracking_ptr class. There is even documentation about how this collection works: http://tinyurl.com/35t2kgy.

Thanks, for the pointer. I will take a look.

Alternatively, you can introduce into your lambda language a special keyword named 'self' to refer to the currently-being-defined function, and define fib as:

 function fib = if_(_1<2) [ _1 ].else_[self(_1-1) + (_1-2)];

This can also be made to work.

I too considered this approach, even had the same name "self" in mind :), or _0(), akin to argv[0] holding the current program name.

If you have the luxury of using C++0x features, you can change your lambda language to look like this:

 auto fib = if_(_1<2) [ _1 ].else_[self(_1-1) + (_1-2)];

Or BOOST_AUTO is also good enough for pre c++0x compilers. But the problem with this is, how can I write mutually recursive functions? I want to be able to say function F1; function F2; F1 = ..refers F2.. F2 = ..refers F1.. This is the main reason I wanted a named type. I am not necessarily married to this syntax. Any other syntax, maybe just using proto mechanism, that allows (mutually) recursive function definitions would be cool..

If you *have* to assign it to a named type, you could either (a) give up on polymorphic lambdas and use something like:

 function fib = ...;

or (b) give up on static type checking and use boost::any in the internal interfaces.

Can you please elucidate (b)? Making the language only have monomorphic lambdas makes it that much less interesting.

It's an interesting problem!

I bet it is. I hope some good ideas come out of discussing this problem. Manjunath