Anonymous recursion: Difference between revisions

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would cause the nest <code>[ dup 1 - recurse ]</code>to be evaluated, and the program would go into a tailspin, recursively evaluating that nest until the return stack overflowed.

This limitation can be overcome with the understanding that recursion can be factored out into two ideas, i.e. self=reference and evaluation. The self-reference word in Quackery is <code>this</code>, which puts a pointer to the current nest on the data stack (usually just called "the stack") and the evaluation word is <code>do</code>, which takes a ~~pointer~~ from the stack and evaluates it. So <code>this do</code> is equivalent to <code>recurse</code>.

This limitation can be overcome with the understanding that recursion can be factored out into two ideas, i.e. self-reference and evaluation. The self-reference word in Quackery is <code>this</code>, which puts a pointer to the current nest on the data stack (usually just called "the stack") and the evaluation word is <code>do</code>, which takes an item from the stack and evaluates it. So <code>this do</code> is equivalent to <code>recurse</code>.

The final example fixes the previous example by ~~putting~~ <code>this</code> at the correct level of nesting and ~~evaluating~~ it within the nested nests ~~with <code>do</code>~~.

The final example fixes the previous example by using <code>this</code> and <code>do</code> to put the pointer to the current nest on the stack at the correct level of nesting and evaluate it within the nested nests.

<pre>[ dup 0 < iff