// refactored to support Lucas sequence initializers function* fib(seed0, seed1) { // * means 'generator' (can also yield*) var hist=[]; if((!seed0 && seed0 !==0) || (!seed1 && seed1 !==0)) { alert("Seed issue: " + seed0 + ", " + seed1 + ". Using 0,1"); seed0 = 0; seed1 = 1; } yield {count:0, value:seed0}; yield {count:1, value:seed1}; hist.push(seed0,seed1); var theSum; var c=2; // simplified while(true){ theSum = hist[c-1] + hist[c-2]; hist.push(theSum); yield {count:c++, value:theSum, ratio:theSum/hist[c-2]}; } } var genFib; // set on first run and reset // --------------- generator above this line ----------- var btnReset, elSeed0, elSeed1; window.onload = function(){ btnReset = document.getElementById("btnReset"); elSeed0 = document.getElementById("seed0"); elSeed1 = document.getElementById("seed1"); elLostPrecisionAt = document.getElementById("lostPrecisionAt"); } var firstGenWithTheseSeeds = true; var firstLine; var unsafeReached; function reset(){ elSeed0.disabled = false; elSeed1.disabled = false; firstGenWithTheseSeeds = true; btnReset.disabled = true; output.innerHTML = ""; output2.innerHTML = ""; elLostPrecisionAt.innerHTML = "---"; } function getInput(){ if(firstGenWithTheseSeeds){ firstGenWithTheseSeeds = false; genFib = fib(Number(elSeed0.value), Number(elSeed1.value)); unsafeReached = false; btnReset.disabled = false; elSeed0.disabled = true; elSeed1.disabled = true; firstLine="SAFE / UNSAFE INTEGER
"; } return document.querySelector("#howmany").value; } function getThisMany(HowMany) { var max=parseInt(HowMany); if(isNaN(max) || max < 1){ alert("Need a parseable, positive number!"); // or runs forever return false; } var output=document.querySelector("#output"); var output2 = document.querySelector("#output2"); var tmp; output.innerHTML += firstLine; firstLine =""; // cheat; no test for (; max>0; --max) { tmp = genFib.next().value; var safe = Number.isSafeInteger(tmp['value']); var colorclass = safe ? 'safe' : 'unsafe'; if(!unsafeReached && colorclass == 'unsafe') { unsafeReached = true; elLostPrecisionAt.innerHTML = tmp['count']; } output.innerHTML += "

" + tmp['count'] + ": " + tmp['value'] + "

"; output2.innerHTML += "

" + tmp['count'] + ": " + tmp['ratio'] + "(" + Math.abs(tmp['ratio'] - (Math.sqrt(5)+1)/2) + ")

"; } } function note(){alert("Generators are re-enterable functions that remember state (like a Python generator, or static class variables).\n\nI only tried up to 1250 at a time (ran 5 seconds). If a batch of 500 (or less) is > 1 second for you, be careful.");}

Fibonacci 'JS generator', custom seeds (Lucas #'s), phi convergence