Tail Recursion in Nodejs

I've talked about tail recursion in a previous post, today I'll show an example on nodejs.

We have a function that sums numbers starting from 0 to an n number.

We have both version of it, the tail recursion and non-tail recursion version:

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function sumNonTailVersion(n) { return (n < 1) ? 0 : n + sumNonTailVersion(n - 1); } function sumTailVersion(n, acc) { acc = acc || 0; return (n < 1) ? acc : sumTailVersion(n - 1, acc + n); }

Use the following code to test the above two functions:

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try { console.log('sumNonTailVersion: ', sumNonTailVersion(1000000)); } catch (e) { console.error('sumNonTailVersion: ', e.message); } try { console.log('sumTailVersion: ', sumTailVersion(1000000)); } catch (e) { console.error('sumTailVersion: ', e.message); }

Run the functions using the following flags:

node --use-strict --harmony-tailcalls file.js

And here's the result:

1 2	sumNonTailVersion: Maximum call stack size exceeded sumTailVersion: 500000500000

The non-tail recursion version fail with "Maximum call stack size exceeded"

Note, if we run without the flags "--use-strict --harmony-tailcalls" the nodejs will run without tail recursion optimizations, and both will treated the same (will through the same error above).