Category: Programming

One of the things I like to do in my spare time is study the STL algorithms. It is easy to take them for granted and easy, perhaps, to imagine that they are mostly trivial. And some are: I would think that any decent interview candidate ought to be able to write find correctly. (Although… Continue reading An algorithmic sketch: inplace_merge

(Start at the beginning of the series if you want more context.) Extras from the Haskell Prelude Having implemented iterate, there were a couple of other useful things from the Haskell Prelude that I wanted to have available with ranges. First, there’s cycle. It simply takes a finite range and repeats it ad infinitum. The… Continue reading Exercising Ranges (part 8)

(Start at the beginning of the series if you want more context.) Calculus operations It’s relatively simple to do differentiation and integration of power series, since they’re just regular polynomial-style. No trigonometric identities, logarithms or other tricky integrals here. Just the plain rule for positive powers of x. For differentiation, we have: [latex]\frac{d}{dx}kx^{n} = knx^{n-1}[/latex]… Continue reading Exercising Ranges (part 7)

(Start at the beginning of the series if you want more context.) Multiplying power series Now we come to something that took considerable thought: how to multiply ranges. Doug McIlroy’s Haskell version of range multiplication is succinct, lazily evaluated and recursive. (f:ft) * gs@(g:gt) = f*g : ft*gs + series(f)*gt Which is to say, mathematically,… Continue reading Exercising Ranges (part 6)

(Start at the beginning of the series if you want more context.) Generalising iota To pretty-print a reversible polynomial, we need to provide for reversibility of iota. So what is iota? It makes a range by repeatedly incrementing a value. What if instead of increment, we use an arbitrary function? We could do this with… Continue reading Exercising Ranges (part 5)

(Start at the beginning of the series if you want more context.) On reversibility It occurs to me that I’ve been touting reversibility as a good thing, both implicitly and explicitly (for polynomials), and the reason for that is not just that I might want to print polynomials in natural decreasing-power-of-x order. The first reason… Continue reading Exercising Ranges (part 4)

(Start at the beginning of the series if you want more context.) So, I was going to implement monoidal_zip, and to do that, I would clone zip_with.hpp. So I did that. Eric’s a great library author, and the ranges code is pretty easy to read. For the most part I found it concise, well-expressed and… Continue reading Exercising Ranges (part 3)

(Start at the beginning of the series if you want more context.) First steps with power series A power series (or polynomial, to give it a more familiar term in the case where it’s finite) is represented simply as a sequence of coefficients of increasing powers of x. This is simple – to represent: [latex]1… Continue reading Exercising Ranges (part 2)

The idea For some time since attending C++Now, I have been meaning to get around to playing with Eric Niebler’s range library. Eric presented ranges in a worked example as one of the keynotes at C++Now – a prior version of the talk that he gave at the Northwest C++ Users Group is currently available… Continue reading Exercising Ranges (part 1)