When did you first try Lisp (meaning here and throughout the survey "any member of the Lisp family") seriously, and which Lisp family member was it?

I had dabbled a bit in Emacs Lisp, Scheme, and Common Lisp, but when I tried Lisp seriously, it was Common Lisp, in 1999.

What led you to try Lisp?

I was working on some hairy C++ code, and according to the profiler, I needed to make it faster. Constantly referring to the assembly output, I rewrote the affected functions and got a significant speed gain. Unfortunately, the resulting code was impossible to follow, and had what looked like an "obvious" bug (even I was tempted to "fix" it, and I knew why it was there!). So, I tried again, and rewrote the code readably, but this time paying close attention to efficiency. Now I had clear, maintainable code that should have been fast, but for one problem -- gcc wouldn't give me as efficient code as I wanted. I knew that the compiler should be free to make certain optimizations on the code, but I had no way of communicating this to the compiler: I had to choose between readability and optimizability.

My solution? I figured that I needed a way to pass promises/hints/transforms to the compiler. I wanted to be able to write my code for human beings, and provide the extra information the compiler needed to transform it into more efficient code. I was already a big fan of Literate Programming, so this seemed like a natural enough desire. I got the gcc source code, and started hacking at it, to give myself the tools I needed. After some success on small examples, I ran into a problem trying to implement what I needed for the production code. It seemed there was a bug in the gcc internals, or maybe I just couldn't understand the code. At this point, I turned to a gcc guru I knew, and asked him if he could help me figure out what was going on.

He was (in retrospect, justifiably) horrified. He pointed out that no one would want to use my custom, hacked C++ compiler, and that I was working hard against the C++ way of doing things. He told me that I should look at Lisp, which is a language that explicitly supports what I was trying to do: its macros are really program-transformations, and it has compiler-macros that are almost exactly what I was (badly) reinventing.

I decided to learn Lisp for real, especially this new world of macros. Skipping past all the cute recursion/closures stuff filling up the beginnings of Lisp books, I picked up Paul Graham's On Lisp, and jumped straight to Chapter 7, "Macros".

If you were trying Lisp out of unhappiness with another language, what was that other language and what did you not like about it, or what were you hoping to find different in Lisp?

C++ promised abstraction, and efficiency, but it could only deliver on one at a time. I wanted to be able to write custom transforms, and generally assist the compiler, so my abstract, readable code would turn into well-tuned machine code.

How far have you gotten in your study of Lisp? (I know, that is hard to measure)

I've gotten quite good at working with Python (the CMUCL/SBCL compiler) to get the machine code I want, from my readable source code. I'm a good, competent applications programmer, and I've worked some in implementation. I still learn things all the time (this is a good thing to me).

What do you think of Lisp so far?

I love it! I still learn new languages, but the desperate search for Something Better is gone. I'm happy using it. I may later discover new Holy Grails that I need to search for, but for now, I've found mine: I can copy pseudo-code out of notes, or papers, and build the Lisp system up to the point where it can run it; not only run the pseudo-code, but do so efficiently.