Have you looked at hindent?

On 11 Oct 2014 11:52 AM, "Oliver Charles" <ollie@ocharles.org.uk> wrote:

Hi all,

It seems that all of the pretty printing libraries on Hackage at the moment have an emphasis on being compact, but not necessarily consistent. By consistent, I mean that similar blocks of code are indented in the same fashion, even when not strictly necessary.

Take for example, the start of "Pretty Printing with Lazy Dequeues". Here, the example is:

if True

   then if True then True else True

   else

      if False

         then False

         else False

I call this inconsistent, because the two sides of the top-level if have been formatted under different rules. A consistent formatting of this would be:

if True

   then 

      if True 

         then True 

         else True

   else

      if False

         then False

         else False

The above can obviously be reached if you *always* format `if` in this style, but that's not what I'm after. If it's possible to format both sides on one-line, then that should be preferred. So an equally desirable output (that meets my "consistency" requirement) is:

if True

   then if True then True else True

   else if True then True else True

It doesn't seem that there is a library on Hackage that lets one express such a pretty printer. It seems that a pretty printer of this nature would need to have some sort of backtracking ability - I can imagine trying to print both sides of the if statement on one-line, and if this fails, try printing *both* on multiple lines.

Curious to hear what people have to say on this matter,

- ocharles

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