Paul Keir schrieb:
> Hi there,
>
> I'm writing a pretty printer using the Text.PrettyPrint library, and
> there's a pattern I'm coming across quite often. Does anyone know
whether,
>
> text (a ++ b ++ c ++ d)
> or
> text a <+> text b <+> text c <+> text d
>
> runs quicker?
Hi Paul,
> text (a ++ b ++ c ++ d)
is the same as
> hcat (map text [a,b,c,d])
(horizontal concatenation without seperating spaces)
while
> text a <+> text b <+> text c <+> text d
corresponds to
> hsep (map text [a,b,c,d])
or
> text (unwords [a,b,c,d])
With <+>, hsep or hcat, pretty printing won't choose the best layout -
you tell the pretty printer to layout documents 'beside'.
For autolayout, see sep,cat and the paragraph-fill variants fsep and fcat.
Regarding performance: `unwords` will propably be a little faster
(untested), but less flexible. There is no asymptotic overhead when
using the pretty printer.
cheers,
benedikt
>
> Cheers,
> Paul
>
>
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