Dave Bayer wrote:

On Jan 23, 2009, at 7:17 PM, Don Stewart wrote:

...

barsoap:

...

I guess everyone knows why.

Use -Wwarn-tabs

It's -fwarn-tabs

I use :set et, always and ever, I don't need to. Think of all those newbies being stuck with strange type errors... Doesn't anyone think of the newbies? ;) -- (c) this sig last receiving data processing entity. Inspect headers for copyright history. All rights reserved. Copying, hiring, renting, performance and/or quoting of this signature prohibited.

But VT is allowed in Haskell. On Sat, Jan 24, 2009 at 10:50 AM, Jon Fairbairn wrote:

Don Stewart writes:

...

barsoap:

...

I guess everyone knows why.

Use -Wwarn-tabs

Warnings are the wrong answer to this problem. In fact, they're rarely the right answer to any problem. Tabs in sourcecode can have bad effects, and Haskell is a language that attempts to reject bad effects as far as possible. Nor can I see any argument in favour of allowing tabs (if HT is allowed, why not VT?).

-- Jón Fairbairn Jon.Fairbairn@cl.cam.ac.uk

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I don't know what you want it to mean, so I can't answer that. :) I doubt anyone has ever used a VT on purpose. I know I haven't. I regard it as a lexical quirk. -- Lennart On Sun, Jan 25, 2009 at 11:07 AM, Jon Fairbairn wrote:

Lennart Augustsson writes:

...

But VT is allowed in Haskell.

Gosh, so it is. It's been a while since I looked, and I've no recollection of the discussion that made it part of whitechar. But does it mean what I want it to mean? Does anyone actually use it? Are there any occurrences of it in Haskell programmes that aren't mistakes?

-- Jón Fairbairn Jon.Fairbairn@cl.cam.ac.uk http://www.chaos.org.uk/~jf/Stuff-I-dont-want.html (updated 2008-04-26)

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Jon Fairbairn wrote:

Warnings are the wrong answer to this problem. In fact, they're rarely the right answer to any problem. Tabs in sourcecode can have bad effects, and Haskell is a language that attempts to reject bad effects as far as possible. Nor can I see any argument in favour of allowing tabs (if HT is allowed, why not VT?).

Tabs can be convenient for quick scripts and things like that, where you wouldn't use -Wall. And while I keep hearing about the problems with tabs, I have never encountered any with Haskell code. There are other things that are currently warnings that come up much more often and usually have much more severe consequences, such as name shadowing. Twan

Achim Schneider writes:

Twan van Laarhoven wrote:

...

Tabs can be convenient for quick scripts and things like that, where you wouldn't use -Wall. And while I keep hearing about the problems with tabs, I have never encountered any with Haskell code.

If you want a key to quickly indent your code, use that funky key with those two arrows, but don't let it produce a tab character while you're editing text. Preferably, let it analyse the syntax of the previous line and automagically Indent By The Right Amount.

Exactly. There's no reason that convenience of input should be part of the language syntax. It's a job for another component. -- Jón Fairbairn Jon.Fairbairn@cl.cam.ac.uk

2009/1/24 Duncan Coutts :

A lot of projects use -Wall. If there is consensus on the tabs issue then we could ask for -fwarn-tabs to be included in -Wall. That should be a good first step. If we cannot achieve consensus within the community for having -Wall include -fwarn-tabs then we have no hope of banning them in the language definition.

So lets first test test the waters on that proposal.

Duncan

+1 for treating tab characters outside comments as a lexical error, and of course if you'd like to add -fwarn-tabs to -Wall first that would be fine with me. - Cale

Johan Tibell wrote:

I do for the following reason: If you use only tabs for leading whitespace you loose the ability to align things. Here's and example using a list (view using a fixed width font):

lst = [1, 2, 3 4, 5, 6]

This definition uses alignment to align the first element on the first line with the first element of the second line. You can't do this kind of alignment using tabs.

Yes, most people use that style or its variations (e.g. when multiple assignments have the equal sign aligned somewhere in the middle of a line or comments are aligned at the end, etc). I do not because when I rename lst to myLst then I need to modify two lines (the second one to fix the alignment). Also I do not like that the change looks bigger in a text diff. I prefer: lst = [1, 2, 3 4, 5, 6] -- fixed indent by two spaces regardless of previous lines Or, if I really care about alignment at such a low level (which I almost never do): lst = [1 ,2 ,3 -- fixed indent by two spaces ,4 ,5 ,6] -- fixed indent by two spaces For your style spaces are the only way to go, what I'm perfectly fine with. Actually whatever way this is resolved, I do not care. Just wanted to point out that there is a use for tabs at the line start ... now thinking it might have been an error :-) Peter.