CyberSpy

Rantings from a guy with way too much free time

Getting func(y) with Channels

Here’s a little golang puzzle

Take a look at the function below that computes a mystery value for the function $f(x)$. Any idea what the function is? Take a close look at the first line where we create a channel. Notice that the channel isn’t some boring int or string channel. No, this is a channel of type func(int, chan int, chan bool). Wait what??? That’s right, this channel takes a function that takes an integer and two channels as function parameters. We define such a function, x, right aftewards.

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Pathocaml - Getting Wacky with Functions And Polymorphism

2018-03-19 Programming Rob Baruch

OCaml on the Fringes - You can do that??

So, I got bored this afternoon and was contemplating why I was enjoying diving into OCaml more than say Elixir/Erlang for functional programming. The quality of the language that’s most captured my attention is the type system.

When you start playing around with the type system in OCaml you can go from some basic definitions of user-defined types to some pretty cool looking constructs. Let’s start of with something pretty transparent and move into something that might actually melt your brain.

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Exercism - Get your Code Deamons Out! Heal Your Body!

2018-02-28 Programming Rob Baruch

Exercis(m)

The best way to keep the mind, body, and soul sharp is to exercise! No better way to learn new programming paradigms than following this same precept when learning new concepts in an unfamiliar programming language. There are several sites online that afford noobs practice problems - Hackerrank, kaggle to name a few. But one that I recently came across, exercism.io, aims to provide not just programming exercises, but a community of folks committed to commenting and sharing both code and criticism on implementations to problem sets across many languages.

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Go Get Interfaced: Enums in Golang

Golang, Interfaces, and Enums

So here’s a nice golang idiom that I ran across years ago that I found generally useful. Golang, unlike languages like c doesn’t natively support enumerations. Instead, constants typically are used when creating a list of enumerations. But, go is a strongly-typed language, so we can do better than simply using constants - we can type our enumeration with the use of a type declaration.

type DogState uint

By defining a type for our enumeration, we can consistently pass and return typed-values among our functions operating on our enumeration. Okay, that’s all well and good, but what happens when we want to go between uint values and string representations of those values; a commonly used paradigm when working with enumerations. One approach would have us write mapping functions that might switch among the values to return a string. Or, when going from a string name of an enumeration to the uint value, we might use a map[string]. That’s a doable implementation, but there’s an easier, and more idiomatic way.

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Gogo

Here we gogo!

Years ago, I wrote an interesting article that I thought might be worth re-posting (and revising) here on my blog. For a while I got into programming in golang and in the early going (pun-alert!), there were a lot of idioms that were not well understood by a noob. One of those paradigms was channels, go-routines, and signals used simultaneously. Taken separately, they are more easily understood. But when taken together, there can be some confusion. In this article, I address how to properly establish a signal-handler and a channel to terminate go-routines when the user interrupts the program with a signal such as ctrl-c or kill(1).

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Recursion Revisited

Recursion, from more than one point-of-view.

A common programming idiom in computer science is solving a problem by self-reference, also known as recursion. In this post, we look at two different implementations of the same problem.

Solve a recursive problem in two different programming language paradigms

Let’s look at the solution to a simple problem, compute $f(x)=e^{x}$.

We will illustrate two separate solutions - one in a procedural language (python), and the other in a functional language (elixir).

Let’s start off with the functional language. Were does recursion come into play?

We define the function $f(x)=e^x$ as the infinite sum, $\text{ }f(x) = \sum_{n=0}^\infty{\frac{x^n}{n!}}$

In our solution below, we define two separate recursive functions, exp/2 and fac/1. What’s interesting to note here is how each of these functions has two separate definitions. This is an aspect of programming in elixir that elegantly uses pattern-matching to return different results depending upon the input. Our two functions nicely dovetail into the base-case and recursive case of a recursive algorithm.

For example, looking at exp/2, the first function definition returns 1 for any value of x (as indicated by the _ preceding the variable) and returns 1. This is the mathematical equivalent of $x^0=1\text{ for any }x$.

The second definition of exp/2 is the recursive case. for any value of $n\gt0$. Moreover, we define exp(x, n) as $\frac{e^x}{n!}$ + exp(x, n-1).

Similarly for the definition of fac/1 we see two definitions; one for $n=0$ and another for all values of $n\gt0$.

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