:~/$ cabal install usb-safe
Resolving dependencies...
cabal: Could not resolve dependencies:
trying: usb-safe-0.14 (user goal)
next goal: base (dependency of usb-safe-0.14)
rejecting: base-4.6.0.1/installed-8aa... (conflict: usb-safe => base>=4 &&
<4.5)
rejecting: base-4.7.0.2, 4.7.0.1, 4.7.0.0, 4.6.0.1, 4.6.0.0, 4.5.1.0, 4.5.0.0,
4.4.1.0, 4.4.0.0, 4.3.1.0, 4.3.0.0, 4.2.0.2, 4.2.0.1, 4.2.0.0, 4.1.0.0,
4.0.0.0, 3.0.3.2, 3.0.3.1 (global constraint requires installed instance)
Dependency tree exhaustively searched.