discard doesn't work about random-js

[dmarku]

I ran into the same issue today and found out that discard() only works when you have generated at least one random number before calling it.

Example Code (using a six-sided die for illustration purposes, as this gives nicer numbers):

var R = require('random-js');

var mt1 = R.engines.mt19937();
mt1.seed(1);
R.die(6)(mt1); // --> 2
R.die(6)(mt1); // --> 6
R.die(6)(mt1); // --> 1
R.die(6)(mt1); // --> 3

var mt2 = R.engines.mt19937();
mt2.seed(1);
mt2.discard(1);
R.die(6)(mt2); // --> gives 2, should be 6
mt2.discard(1);
R.die(6)(mt2); // --> gives 1, so discard works now

var mt3 = R.engines.mt19937().seed(1);
R.die(6)(mt3.discard(1)); // --> gives 2, should be 6
R.die(6)(mt3.discard(1)); // --> gives 1, so discard works now

var mt4 = R.engines.mt19937().seed(1).discard(1);
R.die(6)(mt4); // --> 2, should be 6

As a workaround you can generate a random number first and then discard any remaining numbers:

// return the n-th random number
var R = require('random-js');
function random( seed, n ) {
  var mt = R.engines.mt19937().seed(seed);
  var result = mt();
  if (n > 0) {
    mt.discard(n - 1);
    result = mt();
  }
  return result;
}

The demo code from @dmnd should work with this:

for (var i = 0; i < 10; ++i) {
  console.log(i, random(1337, i));
}

[ckknight]

Sorry for the delay on this one.

[dmnd]

Thanks @ckknight!