+
+-- |'Parser' for an 'HttpVersion'.
+httpVersionP ∷ Parser HttpVersion
+httpVersionP = string "HTTP/"
+ *>
+ choice [ string "1.1" *> pure (HttpVersion 1 1)
+ , string "1.0" *> pure (HttpVersion 1 0)
+ , HttpVersion <$> decimal ⊛ (char '.' *> decimal)
+ ]