codebusters/modulo26.html at main · penguinjeff/codebusters · GitHub

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<html>
<head>
<script>
function doSomething()
{
 const denominator=document.getElementById("denominator").value;
 const decimal=1/denominator;
 const modulo=document.getElementById("modulo").value;
 let frac=0;
 let more=""
 if(!(modulo===""))
 {
  frac=mod26((modulo*1));
 }
 else
 {
  more=" denominator:"+denominator+" decimal:"+decimal+" ";
  frac=mod26(decimal);
 }
 let output=document.getElementById("output");
 output.innerHTML="mod26:"+frac;
}

function mod26(number,denominator=1)
{
 if(denominator===1)
 {
  if(Number.isInteger(number))
  {
   if(number>=0)
   {
    console.log("normal modulo of "+number+" is "+number%26);
	// return (number-(Math.floor(number/-26)*26));
    return number%26;
   }
   else
   {
    console.log("negative conversion of "+number+" is "+(number+(Math.ceil(number/26)*26)));
    // return (number+((Math.floor(number/-26)+1)*26));
    return (number+(Math.ceil(number/-26)*26));
   }
  }
  else
  {
   const n=naive(number)
   if(!Number.isInteger(n))
   {
    console.log(number+" has no modulo 26");
    return;
   }
   console.log("converting decimal "+number+" to 1/"+n);
   return mod26(1,n);
  }
 }
 else
 {
  const smaller=mod26(denominator);
  let val=0;
  switch(smaller)
  {
   case 25: val=25; break;
   case 23: val=17; break;
   case 21: val=5;  break;
   case 19: val=11; break;
   case 17: val=23; break;
   case 15: val=7;  break;
   case 11: val=19; break;
   case  9: val=3;  break;
   case  7: val=15; break;
   case  5: val=21; break;
   case  3: val=9;  break;
   case  1: val=1;  break;
   default:
   console.log("1/"+smaller+" has no modulo 26")
   return;
  }
  console.log("modulo 26 of 1/"+smaller+" is "+val);
  return val;
 }
}

function naive(decimal)
{
 let denominator=1;
 if(decimal>0)
 {
  for(let x=1;x<(25*26);x++)
  {
   if((1/x)===decimal){return x;break;}
  }
 }
 else
 {
  for(let x=-1;x>(-25*26);x--)
  {
   if((1/x)===decimal){return x;break;}
  }
 }
}

</script>
</head>
<body>
1/<input id="denominator" value="1"><br>
<input id="modulo">
<button onclick="doSomething()">process</button>
<div id="output"></div>
</body>
</html>