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Task/Anonymous-recursion/00DESCRIPTION

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+While implementing a recursive function, it often happens that we must resort to a separate "helper function" to handle the actual recursion.
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+This is usually the case when directly calling the current function would waste too many resources (stack space, execution time), cause unwanted side-effects, and/or the function doesn't have the right arguments and/and return values.
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+So we end up inventing some silly name like "foo2" or "foo_helper". I have always found it painful to come up with a proper name, and see a quite some disadvantages:
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+* You have to think up a name, which then pollutes the namespace
+* A function is created which is called from nowhere else
+* The program flow in the source code is interrupted
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+Some languages allow you to embed recursion directly in-place. This might work via a label, a local ''gosub'' instruction, or some special keyword.
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+Anonymous recursion can also be accomplished using the [[Y combinator]].
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+If possible, demonstrate this by writing the recursive version of the fibonacci function (see [[Fibonacci sequence]]) which checks for a negative argument before doing the actual recursion.