Line comment prettyprinting

[athas]

Is there a way to prettyprint something such that every line (when rendered) is prefixed with some string? I looked at how indentation was handled, and it looked like it had to be done as a primitive operator. This would be very useful when prettyprinting languages with line comment syntax.

[mainland]

No, I don't see a way to ensure that each rendered line is prefixed with a string. What do you mean by "line comment syntax?" Can you provide an example? Why can't you post-process the output to add the prefix you want?

[athas]

For example, if I am prettyprinting something with a Haskell-ish syntax, and I want to print some comments using -- comment notation. I don't know how many lines the Doc corresponding to the comment will be rendered as, and just prefixing it with -- won't work if it gets rendered as multiple lines. I could manually render the Doc to a string of (say) 80-character lines, but then the document as a whole will probably not be wrapped properly. It's the best way to do it at the moment, but not optimal.

[mainland]

Look at the way the align combinator is implemented. If you know the printing width, you can use a similar technique to wrap your comment appropriately.