Warning: The install command is a part of the legacy v1 style of cabal usage. Please switch to using either the new project style and the new-install command or the legacy v1-install alias as new-style projects will become the default in the next version of cabal-install. Please file a bug if you cannot replicate a working v1- use case with the new-style commands. For more information, see: https://wiki.haskell.org/Cabal/NewBuild Resolving dependencies... cabal: Could not resolve dependencies: [__0] trying: LambdaHack-0.9.3.1 (user goal) [__1] trying: LambdaHack:-jsaddle [__2] trying: LambdaHack:-vty [__3] trying: LambdaHack:-curses [__4] trying: LambdaHack:-gtk [__5] next goal: sdl2-ttf (dependency of LambdaHack -curses -gtk -jsaddle -vty) [__5] rejecting: sdl2-ttf-2.1.0 (conflict: pkg-config package SDL2_ttf>=2.0.12, not found in the pkg-config database) [__5] rejecting: sdl2-ttf-2.0.2, sdl2-ttf-2.0.1, sdl2-ttf-2.0.0 (conflict: pkg-config package SDL2_ttf>=2.0.0, not found in the pkg-config database) [__5] rejecting: sdl2-ttf-1.0.0, sdl2-ttf-0.2.2, sdl2-ttf-0.2.1, sdl2-ttf-0.2.0 (conflict: LambdaHack -curses -gtk -jsaddle -vty => sdl2-ttf>=2) [__5] fail (backjumping, conflict set: LambdaHack, sdl2-ttf, LambdaHack:curses, LambdaHack:gtk, LambdaHack:jsaddle, LambdaHack:vty) After searching the rest of the dependency tree exhaustively, these were the goals I've had most trouble fulfilling: LambdaHack, sdl2-ttf, LambdaHack:curses, LambdaHack:gtk, LambdaHack:jsaddle, LambdaHack:vty