<+>

(<+>) :: ArrowPlus a => a b c -> a b c -> a b c
base Control.Arrow
(<+>) :: Doc -> Doc -> Doc
template-haskell Language.Haskell.TH.PprLib
Beside, separated by space
(<+>) :: Doc -> Doc -> Doc
pretty Text.PrettyPrint.HughesPJ, pretty Text.PrettyPrint
Beside, separated by space, unless one of the arguments is empty. <+> is associative, with identity empty.