Re: [Haskell-cafe] Pretty-printer for Text

On 27 October 2010 20:13, Stephen Tetley wrote:

On 27 October 2010 09:32, Ivan Lazar Miljenovic wrote:

...

I had to write my own [1] for two reasons: 1) I needed to be able to differentiate between quoted and un-quoted values, and 2) some of the ways values get pretty-printed are different than just "text . show", which is what all the default instances of the Pretty classes are (with the exception of String).  It's this second point that I would wonder how many people would use a default Pretty class: just because I want to print String values one way, does that you mean you should print them that way as well?

If you were specifically working around issues of quoting, maybe there would have been room for an alternative design where an Identifier datatype had two constructors one for simple strings and one for quoted ones.

Well, in my case it's because Dot attributes need to have their values in quotes when they contain spaces, etc. As such, you have these situations: * ` DotNode 1 [Label $ StrLabel "foo"] ' is printed as ` 1 [label=foo] ' * ` DotNode 2 [Label $ StrLabel "bar baz"] ' is printed as ` 2 [label="bar baz"] ' Now, I _could_ have just quoted everything, but I tried to make the generated Dot code as "correct" as possible.

In a nutshell, wl-pprint seems to have got the interface 'right' for my tastes. I like having both named primitive printers and a Pretty class. If I want printers for ShowS types or for Docs that don't need page formatting I always copy Wl-pprint's interface.

OK, I'll keep the class in as well. What about my other queries (e.g. to keep SimpleDoc or not)? -- Ivan Lazar Miljenovic Ivan.Miljenovic@gmail.com IvanMiljenovic.wordpress.com