Resolving dependencies... cabal: Could not resolve dependencies: [__0] next goal: fast-arithmetic (user goal) [__0] rejecting: fast-arithmetic-0.6.0.5 (constraint from user target requires ==0.6.0.4) [__0] trying: fast-arithmetic-0.6.0.4 [__1] next goal: base (dependency of fast-arithmetic) [__1] rejecting: base-4.10.1.0/installed-4.1... (conflict: fast-arithmetic => base>=5 && <5) [__1] rejecting: base-4.11.1.0, base-4.11.0.0, base-4.10.1.0, base-4.10.0.0, base-4.9.1.0, base-4.9.0.0, base-4.8.2.0, base-4.8.1.0, base-4.8.0.0, base-4.7.0.2, base-4.7.0.1, base-4.7.0.0, base-4.6.0.1, base-4.6.0.0, base-4.5.1.0, base-4.5.0.0, base-4.4.1.0, base-4.4.0.0, base-4.3.1.0, base-4.3.0.0, base-4.2.0.2, base-4.2.0.1, base-4.2.0.0, base-4.1.0.0, base-4.0.0.0, base-3.0.3.2, base-3.0.3.1 (constraint from non-upgradeable package requires installed instance) After searching the rest of the dependency tree exhaustively, these were the goals I've had most trouble fulfilling: fast-arithmetic, base