[Haskell-cafe] question about indentation conventions

Sturdy, Ian sturdyi12 at mail.wlu.edu
Mon Jul 1 15:34:56 CEST 2013

I always preferred (I think going back to my lisp days)

    foo x y

indenting subsequent arguments to the same level as the first, but I have not convinced haskell-mode to do that for me. (The general rule here being that similar things should be at the same indent, which will always result in subexpressions being further indented, but is somewhat more specific.)

The case I never quite know what to do with is a series of expressions connected with operators, e.g.

    <|> bar
    <|> baz

Leaving operators at the beginning of lines (rather than trailing the previous line) seems preferable, but does one (where the layout rules apply) align the operator or the function? (the alternative being, if your mail client does not make a mess of it with a variable-width font)

    <|> bar
    <|> baz

From: haskell-cafe-bounces at haskell.org [haskell-cafe-bounces at haskell.org] on behalf of Richard Cobbe [cobbe at ccs.neu.edu]
Sent: Monday, July 01, 2013 8:00 AM
To: haskell-cafe at haskell.org
Subject: Re: [Haskell-cafe] question about indentation conventions

On Mon, Jul 01, 2013 at 05:18:39PM +1200, Richard A. O'Keefe wrote:
> It looked pretty explicit to me:
>       The golden rule of indentation
>       ...
>       you will do fairly well if you just remember a single rule:
>       Code which is part of some expression should be indented
>       further in than the beginning of that expression (even if
>       the expression is not the leftmost element of the line).
> This means for example that
>       f (g x
>           y
>           z)
> is OK but
>       f (g x
>       y z)
> is not.

Sure.  So my first question boils down to which of the two alternatives
below does the community prefer?  (To be clear about the intended
semantics: this is the application of the function f to the arguments x, y,
and z.)

    f x


    f x

Both are correct, in most contexts.

And then there's the second question: if the second alternative is
preferable, is there a way to get haskell-mode to do it automatically?  As
it is, it refuses to indent y any farther to the right than in the first
alternative.  I can space it in by hand, and then haskell-mode puts z under
y, but that's annoying, and it gets in the way of reindenting large regions
of code automatically.


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