It occured to me that boost is lacking a true lazy list. I feel like this should be possible to implement on most compilers, although I doubt I have the metaprogramming expertise to be able to implement such a data structure myself. But nonetheless I think this would be extremely useful. Lazy lists are basically lists that don't store the actual values of the list, instead they store a -function- that is called each time the next element of the list is requested, and the result of that list is returned. Most likely there is a caching mechanism as well, so that accessing recently accessed (or preceding) elements would return a cached value if it had already been accessed. I guess it would not cache arbitrarily large amounts of elements though for memory usage reasons, otherwise it would defeat the whole purpose, which is the ability to expose truly infinite sequences to the user in the form of a list. Has this been considered before, and can anyone think of any technical limitations that would prevent such a class to be written?