Process every pair in a set only once

pair_once.js

// How to do this algorithm in Smalltalk? Call a function on each pair of elements
// in a set once. Do not call func(b,a) if func(a,b) has already been called.

var i,j,ray,func;

ray = [3,2,11,7,5];

func = function(a,b) {
    console.log(a + "x" + b + " -> " + a*b);
};

// For first item, iterate over every item but the last one.
for(i=0; i<ray.length-2; ++i) {
    // For the second item, iterate over every item from i+1 to the end.
    for(j=i+1; j<ray.length-1; ++j) {
        func(ray[i], ray[j]);
    }
}

// Output:

// 3x2 -> 6
// 3x11 -> 33
// 3x7 -> 21
// 2x11 -> 22
// 2x7 -> 14
// 11x7 -> 77

ALso ,not commented, but the code does this, too: don't call func(a,a). (If you want to allow calling func(a,a), change the second loop to start with i=j)