+ highlight_carets no line
+ | no == line1 && no == line2
+ = BS.concat [line, nl, indent, BS.replicate col1 ' ',
+ BS.replicate (col2-col1) '^']
+ | no == line1
+ = BS.concat [line, nl, indent, BS.replicate col1 ' ',
+ BS.replicate (BS.length line-col1) '^']
+ | no == line2
+ = BS.concat [line, nl, indent, BS.replicate col2 '^']
+ | otherwise = line
+ where
+ indent = BS.pack " "
+ nl = BS.singleton '\n'
+