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38 lines
1.2 KiB
Markdown
38 lines
1.2 KiB
Markdown
# Section 1 - recursion
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Let it be said right from the start:
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*Recursion in assembly language is not the ball of joy that it is in
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higher level languages*.
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## Fibonacci Sequence
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The Fibonacci Sequence is one primary example of recursion. Consider
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this example:
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```c++
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unsigned int FibonacciInC(unsigned int nthNumber) {
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if (nthNumber <= 1) {
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return nthNumber;
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}
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return FibonacciInC(nthNumber - 1) + FibonacciInC(nthNumber - 2);
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}
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```
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The terminal condition is `nthNumber` less than or equal to 1. If the
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parameter is less than or equal to 1, the very same value is returned.
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If the parameter is greater than 1, the result is the sum or the
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results of the Fibonacci value of one less than the parameter plus the
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results of two less than the parameter.
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## Recursion Leverages the Stack
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Notice that recursion is accomplished by simply calling a function
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inside itself. All of the work of implementing recursion is hidden
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behind the scenes by the compiler.
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Specifically, `nthNumber` and the results of
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`FibonacciInC(nthNumber - 1)` is pushed onto (and popped off of) the
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stack. The value of `FibonacciInC(nthNumber - 2)` doesn't go on the
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stack because its results are used right away.
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