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Fix variable name #183

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Fix variable name #183

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4 changes: 2 additions & 2 deletions manuscript/ch8.md
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Expand Up @@ -439,9 +439,9 @@ function sum(num1,...nums) {
}
```

This isn't in PTC form because after the recursive call to `sum(...nums)` is finished, the `total` variable is added to that result. So, the stack frame has to be preserved to keep track of the `total` partial result while the rest of the recursion proceeds.
This isn't in PTC form because after the recursive call to `sum(...nums)` is finished, the `num1` variable is added to that result. So, the stack frame has to be preserved to keep track of the `num1` partial result while the rest of the recursion proceeds.

The key recognition point for this refactoring strategy is that we could remove our dependence on the stack by doing the addition *now* instead of *after*, and then forward-passing that partial result as an argument to the recursive call. In other words, instead of keeping `total` in the current function's stack frame, push it into the stack frame of the next recursive call; that frees up the current stack frame to be removed/reused.
The key recognition point for this refactoring strategy is that we could remove our dependence on the stack by doing the addition *now* instead of *after*, and then forward-passing that partial result as an argument to the recursive call. In other words, instead of keeping `num1` in the current function's stack frame, push it into the stack frame of the next recursive call; that frees up the current stack frame to be removed/reused.

To start, we could alter our `sum(..)` function's signature to have a new first parameter as the partial result:

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