Language feature parity and the polyglot programmer

For the average .NET developer, language features in the other .NET language don’t matter 99% of the time.  Unless of course, you’re using a framework designed for features that don’t exist for the language you’re using.

Such is the plight for a Visual Basic.NET developer.

Major “ALT.NET” frameworks simply weren’t designed with VB.NET in mind.  This makes sense, as they are designed and used primarily in C#.  For example, Rhino Mocks makes extensive use of delegates and expressions as method parameters.  VB9 only supports single-line function lambdas, which are anonymous functions that return a value.  VB.NET makes a clear distinction between functions that return a value, with the Function keyword, and functions that don’t return a value, with the Sub keyword.

Basically, the Action family of delegates is severely limited in VB9.

This can make it especially difficult for OSS and other framework developers.  If you’re trying to build an OSS or any other framework for public consumption, do you include both major .NET languages, or target features just for one, usually C#?

I’m leaving out the question for earlier versions of languages, as VS 2008 allows you to target a framework on a project-by-project basis, so any question of “I’m only on C# 2.0” rather moot.

However, looking at the feature specs for VB10, all of these issues have simply disappeared.  With VB10 and C# 4.0, each language team is embracing “co-evolution” going forward, where a major feature added to one language will be added to the other.  In a nutshell, VB10 will include most of the common C# 3.0 features, including:

• Auto-implemented properties
• Single and multi-line anonymous Subs and Functions (i.e., any lambda under the sun)
• Collection initializers

For framework developers, the introduction of VB10 and C# 4.0 mean that the differences between the languages no longer matter.  If you want to build a fluent interface with extension methods, method chaining and nested closures, you no longer need to worry about leaving VB developers behind.

The future polyglot

The polyglot programmer would no longer include the “VB vs. C#” distinction after the VS 2010 release.  Instead, we’ll see a clearer focus on broader language features, such as:

• Static vs. dynamic
• Functional vs. ???
• Scripted vs. compiled

An average web developer today needs to know at least 4 different programming languages:

• Server language (C# or VB.NET for average ASP.NET development)
• HTML
• CSS
• JavaScript

JavaScript, widely used, is so completely different than C#, yet its syntax is similar, that many of the familiar operations you might like to use in JavaScript (such as the “new” operator), are strongly discouraged.  I see the future of development to shift strongly towards a polyglot world, where we’ll use specific languages in circumstances where each language shines, while some languages grow to incorporate more and more features from other worlds.

But what we won’t need to worry about is the difference between the two dominant languages in .NET.