A Heap Of Stuff – a.k.

a.k. from thus spake a.k.

A little over a year ago we added a bunch of basic computer science algorithms to the ak library, taking inspiration from the C++ standard library. Now, JavaScript isn't just short of algorithms in its standard library, it's also lacking all but a few data structures. In fact, from the programmer's perspective, it only has hash maps which use a function to map strings to non-negative integers that are then used as indices into an array of sets of key-value pairs. Technically speaking, even arrays are hash maps of the string representation of their indices, although in practice the interpreter will use more efficient data structures whenever it can.
As clever as its implementation might be, it's unlikely that it will always figure out exactly what we're trying to do and pick the most appropriate data structure and so it will occasionally be worth explicitly implementing a data structure so that we can be certain of its performance.
The first such data structure that we're going to need is a min-heap which will allow us to efficiently add elements in any order and remove them in ascending order, according to some comparison function.

Cuboid Space Division – a.k.

a.k. from thus spake a.k.

Over the last few months we have been taking a look at algorithms for interpolating over a set of points (xi,yi) in order to approximate values of y between the nodes xi. We began with linear interpolation which connects the points with straight lines and is perhaps the simplest interpolation algorithm. Then we moved on to cubic spline interpolation which yields a smooth curve by specifying gradients at the nodes and fitting cubic polynomials between them that match both their values and their gradients. Next we saw how this could result in curves that change from increasing to decreasing, or vice versa, between the nodes and how we could fix this problem by adjusting those gradients.
I concluded by noting that, even with this improvement, the shape of a cubic spline interpolation is governed by choices that are not uniquely determined by the points themselves and that linear interpolation is consequently a more mathematically appropriate scheme, which is why I chose to generalise it to other arithmetic types for y, like complex numbers or matrices, but not to similarly generalise cubic spline interpolation.

The obvious next question is whether or not we can also generalise the nodes to other arithmetic types; in particular to vectors so that we can interpolate between nodes in more than one dimension.