On Fri, 2005-09-23 at 10:55 +0200, Johannes Waldmann wrote:
| test = text "foo" <+> empty <> text "bar" | | Running 'show test' now gives the string "foobar" as a result (whereas I | expected "foo bar").It seems the empty "eats" the space that I expect | <+> to give me.
by definition, x <+> empty == x.
what happens here is related to precedences:
Text.PrettyPrint.HughesPJ> text "foo" <+> empty <> text "bar" foobar Text.PrettyPrint.HughesPJ> text "foo" <+> ( empty <> text "bar" ) foo bar
Thank you for your answer. That does make some sense. On the other hand, I am not sure I think this behaviour is reasonable. I think these two should be equivalent: Text.PrettyPrint.HughesPJ> text "foo" <+> empty <> text "bar" foobar Text.PrettyPrint.HughesPJ> text "foo" <+> text "" <> text "bar" foo bar I argue that (text "" == empty) and that I should be able to use them synonymously. The point I think I'm trying to make is that I have used this pretty printing library for a while now, and I have never had to worry about the precedence of the operators before. As Simon pointed out the library could use some improvement, but with my current workload this is certainly not something I can do. Another idea would be replacing Text.PrettyPrint.HughesPJ with some other pretty printing library. Some very shallow searching reveals this[1] which seems to be an improvement on what we have today. Cheers, Anders [1] http://www.cs.uu.nl/~daan/pprint.html