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Who Needs Garbage Collection?Here is the idea: Popular wisdom dictates that functional languages need garbage collection, but is it really true. For example C++ style move semantics seem to solve the problem of returning a closure from a function, you create an object to contain a copy of all the local variables and functions, and then swap the local copy of the handle with the calling functions allocation, so when the function returns it destroys the empty handle from the caller, leaving the caller with the handle to the closure. On this basis any acyclic datatype can be stored in the heap, but its lifetime managed from the stack handle (this is what RAII is doing in C++ STL). I guess this is a degenerate case of reference counting, where we limit references to two types, a unique 'owning' reference (lets call it a handle to disambiguate) , that when it goes out of scope releases the memory (its unique and un-copyable so no need to count references), and an 'ephemeral' reference (lets call it a pointer) that is restricted in that it cannot be 'leaked' to a scope more short lived than the scope in which the handle exists. This all sounds a lot like Ada access variables - but note the change from the scope in which the handle was created, to the any scope in which the handle exists, as returning handles by move semantics is possible. This allows a constructor to return a handle into a scope which is also allowed to hold pointers to the object. It doesn't sound like it really needs anything new, just a combination of Ada's access variable, and the mechanism for converting closures into objects described above. What potential problems might there be? Could this work, or is there some overlooked flaw? By Keean Schupke at 2014-07-25 13:07 | LtU Forum | previous forum topic | next forum topic | other blogs | 39493 reads
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