I realize this is a topic where it would be very easy to start a flame war, but hopefully we can avoid that. Paul Hudak wrote:
Why not have your tool generate layout-less code? Surely that would be easier to program, and be less error prone.
The tool in question is Happy, and the error materialized as an interaction between the tool-generated parser code and the hand-written code in actions. So no, this was not an option since the tool is not written by me, and given my current capabilities in Haskell I could not even fix it. On the other hand the bug is easy to work around, and it might even be fixed in newer versions of Happy.
Yes, but the layout is not ENFORCED. I programmed in Lisp for many years before switching to Haskell, and a common error is something like this:
(let ((a 0) (b 1) (+ a b)))
In this case the error is relatively easy to spot, but in denser code it can be very subtle. So in fact using layout in Lisp can imply a semantics that is simply wrong.
Maybe I did not express my point clearly. What I was trying to say was that because of the syntax, it is very easy for M-C-q in Emacs to convert that to (let ((a 0) (b 1) (+ a b))) which brings the layout of the source code to agreement with how it is perceived by the compiler/interpreter. So it is easy for me to enforce the layout. This is not so much of an issue when you are writing the code in the first place, but I find it a pain to have to adjust indentation when I move bits of code around in an evolving program. If there is good support for that, then I'll just shut up an start using it. After all, I have only been using Haskell for a very short period of time. -- pertti