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select-test.js
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select-test.js
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var vows = require("vows"),
assert = require("assert"),
crossfilter = require("../");
var suite = vows.describe("select");
suite.addBatch({
"heapselect": batch(crossfilter.heapselect)
});
function batch(select, extras) {
var batch = {
topic: function() {
return select;
},
"can select from a small array of positive integers": function(select) {
var array = [6, 5, 3, 1, 8, 7, 2, 4];
assert.deepEqual(select(array, 0, array.length, 1), [8]);
assert.deepEqual(select(array, 0, array.length, 2).sort(descending), [8, 7]);
assert.deepEqual(select(array, 0, array.length, 3).sort(descending), [8, 7, 6]);
assert.deepEqual(select(array, 0, array.length, 4).sort(descending), [8, 7, 6, 5]);
assert.deepEqual(select(array, 0, array.length, 5).sort(descending), [8, 7, 6, 5, 4]);
assert.deepEqual(select(array, 0, array.length, 6).sort(descending), [8, 7, 6, 5, 4, 3]);
assert.deepEqual(select(array, 0, array.length, 7).sort(descending), [8, 7, 6, 5, 4, 3, 2]);
assert.deepEqual(select(array, 0, array.length, 8).sort(descending), [8, 7, 6, 5, 4, 3, 2, 1]);
},
"does not affect the original order; returns a copy": function(select) {
var array = [6, 5, 3, 1, 8, 7, 2, 4];
select(array, 0, array.length, 4);
assert.deepEqual(array, [6, 5, 3, 1, 8, 7, 2, 4]);
},
"returns fewer than k elements when k is too big": function(select) {
var array = [6, 5, 3, 1, 8, 7, 2, 4];
assert.deepEqual(select(array, 0, array.length, 8).sort(descending), [8, 7, 6, 5, 4, 3, 2, 1]);
},
"returns an empty array when selecting nothing": function(select) {
var array = [];
select = select.by(function(d) { return d.value; });
assert.deepEqual(select(array, 0, array.length, 1), []);
},
"the returned array is a binary heap": function(select) {
var array = [6, 5, 3, 1, 8, 7, 2, 4];
for (var i = 0; i < 10; ++i) assert(heapy(select(array, 0, array.length, i)), array + "");
}
};
for (var key in extras) batch[key] = extras[key];
return batch;
}
function descending(a, b) {
return a > b ? -1 : a < b ? 1 : 0;
}
function heapy(array) {
var n = array.length;
for (var i = 1; i < n; ++i) {
if (array[i] < array[i - 1 >> 1]) {
return false;
}
}
return true;
}
suite.export(module);