Programming with floating point is always fun. Here's a nice little screen capture summarizing the insanity that sometimes arises: .NET keeps 9 digits of precision internally, but typically only displays 7 digits of precision, so I had a hell of a time figuring out why a value from what's effectively a no-op was exceeding the 0.33F threshold I was looking for. Losing equational reasoning is always…
I typically keep this blog about computer science, but I also dabble in a bit of philosophy. I was initially struck by Bostrom's simulation argument when I first read it years ago. Over the years, I've cycled a few times between disputing what I believed were some of its assumptions, and cautious acceptance after realizing my mistake. The simulation argument in its simplest form is that one of the…
In my last two posts on automatic differentiation (AD), I described some basic primitives that implement the standard approach to forward mode AD using dual numbers, and then a dual representation of dual numbers that can compute in reverse mode. I'm calling these "co-dual " numbers, as they are the categorical dual of dual numbers. It didn't click at the time that this reverse mode representation…
Continuing from my last post on implementing forward-mode automatic differentiation (AD) using C# operator overloading , this is just a quick follow-up showing how easy reverse mode is to achieve, and why it's important. Why Reverse Mode Automatic Differentiation? As explained in the last post, the vector representation of forward-mode AD can compute the derivatives of all parameter…
I've recently been researching optimization and automatic differentiation (AD) , and decided to take a crack at distilling its essence in C#. Note that automatic differentiation (AD) is different than numerical differentiation . Math.NET already provides excellent support for numerical differentiation . C# doesn't seem to have many options for automatic differentiation, consisting mainly of an F#…
More adventures in C, I revisited my exception handler implementation libex . I realized there's an even simpler version that's more efficient if we give up the requirement that exceptions can be propagated to callers: #define TRY #define THROW(E) goto E #define CATCH(E) goto FINALLY_H; E: #define FINALLY FINALLY_H: This implementation requires only a single exception handling block per function,…
The async/await idiom is becoming increasingly popular. The first widely used language to include it was C#, and it has now spread into JavaScript and Rust. Now C/C++ programmers don't have to feel left out, because async.h is a header-only library that brings async/await to C! Features: It's 100% portable C. It requires very little state (2 bytes). It's not dependent on an OS. It's a bit simpler…
I recently built a REST API prototype where one of the endpoints accepted a string representing a filter to apply to a set of results. For instance, for entities with named properties "Foo" and "Bar", a string like "(Foo = 'some string') or (Bar > 99)" would filter out the results where either Bar is less than or equal to 99, or Foo is not "some string". This would translate pretty…
I've finally updated Sasa to target .NET standard 1.3, removed a lot of superfluous abstractions, and rewrote some of the existing API to target third-party packages that are better supported. This may be the last stable release of Sasa, since I'm shifting. Fortunately, the remaining Sasa features are very stable so there's not much need to evolve them further. You can find the full API…
In playing around with Razor Pages, I was irritated again that Microsoft couldn't just standardize a set of interfaces for their methods so that they wouldn't need so much magic. So I just quickly hacked up RazorInterfaces , available also on nuget.org . It's probably most useful to people just learning Razor Pages, since it requires you to correctly implement the common HTTP methods you'll need…
After a long hiatus, I'm slowly starting back on blogging and some personal projects. To get me back in the swing of things, here's a short post on running ASP.NET core on Google Cloud, since this seems poorly documented online. The default project created by the Google Cloud tools includes Microsoft.AspNetCore.All which is a huge dependency. If you want something more minimal: uninstall-package…
A thread on reddit pointed to Canada's consultation on what sort of legislative framework they should create to facilitate investigations in the digital world. Many of the questions are leading and borderline deceptive in their phrasing, but if we're being charitable, this is a good opportunity to inform policy makers. To that end, these are my responses: How can the Government address challenges…
There are plenty of tutorials online for creating tabbed panels in HTML documents, some using JavaScript, some using pure CSS tricks. Most of the approaches seem to assume that a list of some type is the appropriate element to use for a tabbed interface, but I'd argue that lists are not semantically descriptive of tabbed interfaces. They either include the main tab content along with the tab name,…
In any system with mutable entities saved in an object store, it's inevitable that you'll want to audit the changes made to a particular entity. Explicitly versioning your entities solves this problem, and it's often pretty useful to end users of a sophisticated application, say for undo purposes. However, it's not always so clear how to transform a mutable entity into an versioned entity. There…
I just wanted to jot down some thoughts on compiling eval/apply curried application using an efficient register-based calling convention. This translation is actually quite simple once you get the trick. Leroy's Zinc abstract machine showed the way: evaluate arguments right-to-left instead of the typical left-to-right. The ZAM wrote these arguments to a stack, but in our case we want them to go to…
Algebra.NET is a simple library designed to facilitate easy expression and manipulation of algebraic functions. For instance, here's a simple function: Function<Func<double, double>> a = Algebra.Function(x => 2 * x + 1); We can compile such a function to efficient IL: Func<double, double> func = a.Compile("times2plus1"); Or we can apply some algebraic identities to rewrite it: Identity associative…
A few new features in this release, and a few bugfixes and enhancements in MIME parsing. As before, the online docs are available on my site, the full release including experimental assemblies on Sourceforge , and the production assemblies on Nuget . The changelog: * sasametal can now replace columns and FK associations with enums that are provided separately * sasametal can now output an…
Just a bugfix release, mainly for the MIME parsing. Changelog: * added support for 8bit transfer encoding, even if not supported by .NET <4.5 * support content types whose prologue is empty * added support for arbitrarily nested multipart messages * added alternative to Enum.HasFlag that invokes Sasa's faster enum code As usual, online docs are available , or the a CHM file is available on…
I've had numerous posts here describing instances where C# has come so close to getting it right, and yet misses the mark by an inch. The original C# enums have a simple semantics: enum SomeEnum { First, // compiler implicitly assigns 0 Second, // compiler implicitly assigns 1 Third, // compiler implicitly assigns 2 Fourth, // compiler implicitly assigns 3 } This worked nicely as a concise…
Mainly a bugfix release, with only a few new features. As always, the docs are available here online , or as a compiled CHM file on sourceforge . Here's the changelog: * a few bugfixes to MIME parsing for header and word decoding (Thanks Evan!) * added combined SubstringSplit function for more space efficient parsing * explicitly parse e-mail addresses for more flexible address separators *…
This release features a few new conveniences, a few bugfixes and a vector that's faster than any other I've managed to find for .NET. Here's the changelog since the last v0.14.0 release: * more elaborate benchmarking and testing procedures * added a minor optimization to purely functional queues that caches the reversed enqueue list * FingerTree was switched to use arrays as opposed to a Node type…
The µKanren paper is a nice introduction to a lightweight logic programming language which is a simplification of the miniKanren family of languages. The existing µKanren implementation in C# was a translation from Scheme, and thus is verbose, untyped with lots of casts, and non-idiomatic. I also found most of the other Kanren implementations unnecessarily obscure, heavily relying on native idioms…
NHibernate is a pretty useful tool, but occasionally it's not entirely documented in a way that makes it's flexibility evident. Composite keys are a particularly difficult area in this regard, as evidenced by the numerous articles on the topic. Most of the existing articles cover this simply enough, but there is one uncommon corner case I have yet to see explained anywhere: a composite primary key…
.NET's delegates are a powerful and convenient abstraction available since .NET 1.1. They encapsulate a method pointer and the object the method belongs to in a single callable "function object". Multicast delegates are an extension of plain delegates, in that they encompass multiple single delegates. Invoking a multicast delegate invokes every encapsulated delegate, in the order they were added.…
A quick release, fixing one bug and adding some performance improvements and some new collection types. Here's the changelog: * added a faster and more compact hash array mapped trie under Sasa.Collections.Trie to replace Sasa.Collections.Tree * added Sasa.Collections.FingerTree * added purity attributes throughout Sasa (for .NET 4) * expanded various test suites and documentation * added a…