creating permutations

[BillFoster]

I need permutations of [0,1,..,n-1]

So I tried to use the function, deal in math.js. First I had to include it in jme.js, along with randomint

new funcObj('randomint', [TNum], TNum, math.randomint); new funcObj('deal', [TNum] , TList , math.deal);

randomint works but not deal

I then rewrote it as

//returns a random number in range [0..N-1]
randomint: function(N) {
    return Math.floor(N*(Math.random()%1)); 
},

//a random shuffling of the numbers [0..N-1]
deal: function(N) 
{ 
    var J, K,L,  Q = new Array(N);
    for(var i=0;i<N;i++)
    {
        Q[i]=i;
    }
    for (J=0 ; J<N -1; J++)
        { K = J+math.randomint(N-J) ; L=Q[J] ; Q[J]= Q[K] ; Q[K] = L; }
    return Q; 
},

Still doesn't work.

If I ask for {deal(4)} I get [ , , , ]

Any obvious errors?

[christianp]

When you're constructing a TList, your list needs to contain TNum objects, not just normal javascript numbers. I've just committed a JME implementation of the deal function which does the conversion for you.

It would probably be good manners if the TList constructor did the conversion for you.

[BillFoster]

Thanks

-----Original Message----- From: Christian Perfect [mailto:reply+i-3374117- 16fe5c4925ff40455d76f208222804c7dc251af6-750780@reply.github.com] Sent: 24 February 2012 3:50 PM To: Bill Foster Subject: Re: [Numbas] creating permutations (#142)

When you're constructing a TList, your list needs to contain TNum objects, not just normal javascript numbers. I've just committed a JME implementation of the deal function which does the conversion for you.

It would probably be good manners if the TList constructor did the conversion for you.

---

Reply to this email directly or view it on GitHub: https://github.com/numbas/Numbas/issues/142#issuecomment-4159050