On Nov 17, 2007 3:04 PM, apfelmus
Unfortunately, I don't have Paulson's book (or any other ML book :) at home. I'm too lazy to figure out the specification from the source code,
I guess the code is too opaque, as my colleague claimed. The layout the algorithm generates condensed indented blocks. Within a block, it inserts a newline when the distance to the next break point plus the current position is greater than the space remaining on the current line. Thus if S-Expression lists are rendered as blocks with indent two, and every element in a list is separated by a break point of length one, with the proper margin, you would see: (defthingy name-of-thingy (one thing) (two thing) (a-big-thing-made-bigger) (three thing) (four thing)) As an exercise, the book asks you to implement group indent, where if any break point in a group inserts a newline, they all do. So with that layout, one would get: (defthingy name-of-thingy (one thing) (two thing) (a-big-thing-made-bigger) (there thing) (four thing)) The C version I wrote supports this layout, but I didn't bother with that extension for the Haskell version. On the strictness annotations, my reasons for them are the usual ones, primarily to prevent memory leaks due to dragging, but a performance boost is always welcome. At some point, I plan to profile the code with and without the annotations, and find out where they are needed. John