gistfile1.clj

(def playlist
[{:title "Elephant", :artist "The White Stripes", :year 2003}
{:title "Helioself", :artist "Papas Fritas", :year 1997}
{:title "Stories from the City, Stories from the Sea",
:artist "PJ Harvey", :year 2000}
{:title "Buildings and Grounds", :artist "Papas Fritas", :year 2000}
{:title "Zen Rodeo", :artist "Mardi Gras BB", :year 2002}])

; (group-by :artist playlist) returns:

;= {"Papas Fritas" [{:title "Helioself", :artist "Papas Fritas", :year 1997}
;= {:title "Buildings and Grounds", :artist "Papas Fritas"}]
;= ...}

; desired:

;= {"Papas Fritas" [{:title "Helioself", :year 1997}
;= {:title "Buildings and Grounds"}]
;= ...}

; from http://www.clojurebook.com/