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Stack-safety for free?
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// This gist contains the JavaScript version of the code from the blog post | |
// https://hurryabit.github.io/blog/stack-safety-for-free/ | |
function triangular(n) { | |
if (n == 0) { | |
return 0; | |
} else { | |
return n + triangular(n - 1); | |
} | |
} | |
function trampoline(f) { | |
function mu_f(arg) { | |
const stack = []; | |
let current = f(arg); | |
let res = undefined; | |
while (true) { | |
const { done, value } = current.next(res); | |
if (!done) { | |
stack.push(current); | |
current = f(value); | |
res = undefined; | |
} else { | |
if (stack.length > 0) { | |
current = stack.pop(); | |
res = value; | |
} else { | |
return value; | |
} | |
} | |
} | |
} | |
return mu_f; | |
} | |
const triangular_safe = trampoline(function* (n) { | |
if (n == 0) { | |
return 0; | |
} else { | |
return n + (yield (n - 1)); | |
} | |
}); | |
const LARGE = 100_000; | |
console.clear(); | |
if (triangular_safe(LARGE) != LARGE * (LARGE + 1) / 2) { | |
throw Error("`triangular_safe` computed wrong value."); | |
} | |
console.log("`triangular_safe` has not overflowed its stack."); | |
console.log("`triangular` will overflow its stack soon..."); | |
try { | |
triangular(LARGE); | |
throw Error("`triangular` has not overflowed its stack."); | |
} catch (exc) { | |
if (exc.message.includes("call stack")) { | |
console.log("`triangular` has overflowed its stack.") | |
} else { | |
throw exc; | |
} | |
} |
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