test.clj

(def
  ^{:doc "Map between the second digit in a MODIS TileID metadata
value and the corresponding resolution of the tile data."}
  res-map
  {"1" "1000"
   "2" "500"
   "4" "250"})

(defn tileid->res
  "Returns a string representation of the resolution (in meters) of
the tile data referenced by the supplied TileID.The second character
of a MODIS TileID acts as a key to retrieve this data."
  [tileid]
  (res-map (subs tileid 1 2)))

;; OR!
(defn tileid->res
  "Returns a string representation of the resolution (in meters) of
the tile data referenced by the supplied TileID.The second character
of a MODIS TileID acts as a key to retrieve this data."
  [tileid]
  (let [s (subs tileid 1 2)]
    (cond "1" "1000"
          "2" "500"
          "4" "250")))