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I, Tim Kerchmar, do solemnly offer these my responses to The Road to Lisp Survey:

When did you first try Lisp seriously, and which Lisp family member was it? In September 2005, I finally made the plunge into actual Lisp programming. I had been a longtime lurker on comp.lang.lisp and read Paul Graham's essays and Practical Common Lisp. I wanted an affordable version of Lisp that was suitable for an indie game developer. I purchased Corman Common Lisp and I have been pleased with his excellent support and speedy FFI.
Many of us had multiple run-ins with Lisp before it "stuck". The "stick" date is of most interest, but you can share earlier encounters if you like.

I used a product called CodeSmith that reworks the ASP.NET syntax to autogenerate code and integrates with the build process. I also created a pretty cool XML->CPP converter for one of my earlier game engines. Metaprogramming has always fascinated me, since it smells silver bulletish. Those metaprogramming techniques are inflexible and overly complicated compared to Lisp macros. When I finally "got it", I was stuck, even though it took me a few weeks to find a promising implementation of Lisp.

What led you to try Lisp?

Let me share one little idiom that I find annoying and difficult to work around in other languages. How many times have you had to iterate through a list, accumulating a second list of objects, and then iterating through that second list to delete items from the first list, because the list iterator becomes invalid if you try to remove its item from the list? In Lisp, I can hold a pointer to my current cons cell, whose cdr still points to the remainder of the list, even after calling (setf mylist (remove item mylist). The garbage collector has often allowed me to write elegant solutions for things that never should have been complicated.

What other languages have you been using most?

I work for a major middleware provider in the games industry, and we are strictly of the Church of C++. My coworkers are the best programmers that I've had a chance to work with in a commercial setting, and it pains me to see their "clever" use of templates + #defines... My 10 years of C/C++ did not produce a desire to overcome and master the pointer, but a hatred of the despicable things. Lisp has saved me, by somehow combining pointer and beauty, in a way that my intuition knew existed all along.

How far have you gotten in your study of Lisp? Far enough to have this pretty cool setup where I can start Visual Studio 2003, launch my C++ DLL project, which starts CormanLisp.exe as the parent process. Then I start my physics engine inside Corman Lisp, and it calls the DLL, which then passes callbacks back to Lisp. I can now debug simultaneously in both Lisp and C++ on the same project. One part does all the hairy DX9 stuff, the other part handles the elegant physics stuff, and if any failure occurs, I can know about it! Ok, ok! So I'm not one of those SICP kinds of people. I read those kinds of books about using Lisp to make a DSL in Lisp, and my mind starts wandering. I want to write games faster, maybe fast enough to finish them before I get bored of writing them. So far, Lisp is holding my interest, and I am slowly starting to write Lisp in Lisp instead of C++ in Lisp. Macros and functions as values have already proven very helpful. #define and the C function types always were so ugly.

What do you think of Lisp so far?

In a sense, Lisp is like quiet classical music. You don't even notice it because you are getting work done, but for some reason you are feeling productive and motivated. One funny thing is that I can more accurately estimate how much effort a task will take. The problem is that the barrier to adding new features is so little that I usually still spend too much time, but I did stuff that I didn't even think of when I started. :-) I was afraid that Lisp is slow, or not fast enough for real time applications. I now think that I was backwards. Corman Common Lisp's garbage collector is very speedy. It is so easy to make global modifications to a program, the kind of modifications that are particularly painful in C++, that my program runs 50x faster than the naive implementation of the same program in C++. Oh yes, this program is a 2D physics engine, the real deal with number crunching, and using lists (not vectors!) for everything. Interestingly enough, I also think that a compacting garbage collector may provide such good cache coherency compared to malloc/new that it pays for itself.

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Switch Date 2005

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