Monday, August 25, 2014

Lua is small and small is beautiful

Lua is a tiny language and like C has a tiny standard library. Like many other users of Lua, there are times when I wish it had some language feature (ability to specify types, for example) - but when I think about who Lua is meant for by its designers, I get the logic behind keeping it really small and simple.

Although Lua is powerful enough as a language that it can be used for many complex tasks - see DynASM for an assembler written in Lua - its primary design goal is to provide applications with an extension language. So for example you have a Spreadsheet application, and you wish to allow users to write their own functions they can use in the Spreadsheet. Or you have a Editor and you wish to allow users to customise the editor. And so on. In all these use cases, we cannot assume that the end user who is coding in Lua is a competent programmer. Hence Lua needs to be ultra-simple for such users. Having types in the language, for example, would immediately complicate the syntax of Lua.

That Lua fulfils the needs of its users is evident from the fact that a number of attempts have been made to create a Lua clone that is more powerful as a language - but none of these alternative improved Lua clones have any great following (Note that I exclude LuaJIT from this list as it is 100% faithful to Lua 5.1 so it is another implementation of Lua rather than a clone). I guess the question you have to ask is:

  • Are you trying to create an extension language for ordinary users who are not programmers?

If not then perhaps Lua is not the language you need. 

Tuesday, August 05, 2014

Lua - A fabulous programming language

Last year I discovered Lua and LuaJIT.

These are both amazing implementations of the programming language Lua.

Ok now I need to explain why I think Lua is fabulous and these implementations are amazing.

Lua is a very small, dynamic, scripting language that is extremely easy to learn, and that can be used standalone as well as an embedded scripting language. The well documented and well crafted C API for extending the language is probably one of the best features of the Lua system.

It takes less that a minute to compile and build the Lua language and its basic libraries. Since the language is written in ANSI C, you can virtually build it on any platform.

LuaJIT is a JIT implementation of Lua created by a guy called Mike Pall who is without a doubt a programming wizard. LuaJIT features an interpreter that is hand-crafted in assembler, and has an amazing FFI library that allows easy extensions in C, including creating new data types. LuaJIT comes with an assembler called DynASM that is itself written in Lua.

Neither of these implementations depend on third-party libraries or tools ... which is an amazing thing in today's world (just look at the dependency list of Julia for comparison).

I hope to use Lua extensively in the future, so much so that I decided to learn assembler in order to be able to understand LuaJIT better.

Friday, August 01, 2014

Should you ever embark on a complete rewrite?

I embarked on V2 of my project SimpleDBM about 3 years back. Finally last month I closed down the V2 branch and merged the useful stuff back into the main branch.

V2 was going to be a major refactoring of the system. That is what killed it - because any major refactoring is large amount of effort. One of the best write ups on why no one should ever do this is this article at Joel on Software.

That doesn't mean one should not refactor software - it is just that small incremental changes that are immediately merged and tested with the mainline is the better way to do it.

SimpleDBM is now licensed under Apache License 2.0

I am pleased to announce that as of v1.0.23 the license is changing to Apache License 2.0. The new release is available in Maven Central.

See my earlier post for the rationale for this change.

Sunday, July 27, 2014

Life after Java

After working exclusively in Java for several years, I have been dabbling in C++ for the last year or so.  Question arises - is C++ still a viable language? If Tiobe Index is to be believed C++ has been steadily declining in popularity since about 2005 - coincidentally this was the year I decided to move from C++ to Java for my project SimpleDBM. At the time I stated my reasons for the move in my second blog post.

So what has happened in the meantime and is C++ still a viable language?

The place where I work (my day job) - I introduced Java in the realm of financial risk analytics. I led the team that converted a C++ based application to Java - and in the process we proved that the Java implementation was several times faster. The reason for this was nothing to do with the choice of the language - it was just that with Java you can focus on better algorithms and data structures, rather than fighting the language - which made all the difference in my view.

And yet it is in the realm of numerical computing where C++ is arguably the best language with the exception perhaps of Fortran (of which I have no experience sadly). The main advantages of C++ are:
  • Ability to seamlessly call C++, Fortran and C libraries - a lot of high performance numerical libraries out there are written in these languages.
  • Control of memory layout of data structures.
  • Efficient array access via pointers - and no bounds checking.
  • Templates for generating type specific code.

C++ is still an ugly language with too many features - but the recent changes in C++ 11 have made life tolerable if not completely easy. I have been looking at alternatives such as D, Go, Julia, etc. but haven't found a viable alternative yet. These other languages are either immature or have very restrictive paradigms. JVM based languages such as Scala have the same issues essentially as Java.