Simon Michael wrote:

...

Does that help?

It helps me a lot. I never clearly understood that there are these two different layout modes in my code (coddled by haskell-mode!) This will cut down some more guesswork. Thanks!

There is a new indentation module which does much better at the indentation stuff: http://kuribas.hcoop.net/haskell-indentation.el Jules

On Wed, Oct 15, 2008 at 5:25 PM, Jules Bean wrote:

There is a new indentation module which does much better at the indentation stuff:

http://kuribas.hcoop.net/haskell-indentation.el

I didn't realize until I tried to use yours that there are two indentation modules in haskell-mode, and I'd been using the inferior one. This does mean I can't tell what changes you have made, though. If it's not too much trouble, could you summarize your changes? Also, is this code going to make it into haskell-mode proper, or are there issues preventing that? If the latter, I wouldn't mind having a darcs repository to pull from.

Basically it has a more accurate haskell parser, and it has a simpler way of cycling through possible indentations: TAB moves to the right and BACKSPACE to the left.

Unfortunately, it can sometimes fail to parse what's in the buffer, get balky and event prevent you typing anything at all. I had to back out of it for now..

Thanks Jules and Daniel. That was very helpful. Regards -Vivek Ramaswamy- -----Original Message----- From: Jules Bean [mailto:jules@jellybean.co.uk] Sent: 15 October 2008 18:19 To: Ramaswamy, Vivek Cc: haskell-cafe@haskell.org Subject: Re: [Haskell-cafe] Haskell newbie indentation query. Ramaswamy, Vivek wrote:

Hello All~

I have just started with Haskell, and I must confess; I am in love with it.

However one area that I am really confused about is indentation.

Lets take a look at if-else if- else block.

Important point 1. There are two contexts in haskell programs. Layout and non-layout. In a non-layout context you can do whatever you like with indentation. You can put the newlines wherever you want. In practice, almost everyone uses layout for the 'top-level' of a module. That means that anything flush to the left margin starts a new declaration. However, making sure we are not flush to the left margin, the following are all fine x = if True then 1 else 2 x = if True then 1 else 2 x = if True then 1 else 2 x = if True then 1 else 2 because, layout is not relevant in expressions. Now, "do blocks" are layout blocks. So what you really want us to look at is the use of if/then/else in do blocks. x = do if True then (return 1) else (return 2) The first line in the do block defines the left margin for this block. In this example, the first line is the "if" line, that defines the left margin. Since the "then" and the "else" are also both on the left margin, they are new statements. So, the layout interprets as: do {if True; then (return 1); else (return 2)} ...which is a parse error, because a statement cannot begin with 'then' or 'else'. any pattern of indentation which keeps the if expression indented further to the right will be OK, such as x = do if True then (return 1) else (return 2) x = do if True then (return 1) else (return 2) ..are both fine. Does that help? Jules