convert :: (Double, [Char]) -> (Double, [Char])
convert (n, unit) 
	|unit == "m"    = (n * 1.09361, "yd")
	|unit == "yd"   = (n / 1.09361, "m")
	|unit == "L"    = (n * 0.264172, "gal")
	|unit == "gal"  = (n / 0.264172, "L")
	|unit == "kg"   = (n * 2.20462, "lb")
	|unit == "lb"   = (n / 2.20462, "kg")
	|otherwise      = (n, "unrecognized input")

main = print $ convert (4, "L")