Resolving dependencies...
cabal: Could not resolve dependencies:
next goal: regex-pderiv (user goal)
rejecting: regex-pderiv-0.1.3, 0.1.2, 0.1.1, 0.1.0, 0.0.9, 0.0.8.2, 0.0.8.1,
0.0.8, 0.0.7 (global constraint requires ==0.0.6)
trying: regex-pderiv-0.0.6
trying: base-4.7.0.1/installed-e4b... (dependency of regex-pderiv-0.0.6)
rejecting: regex-pderiv-0.0.6:+base4 (conflict:
base==4.7.0.1/installed-e4b..., regex-pderiv-0.0.6:base4 => base>=4.0 &&
<=4.1)
rejecting: regex-pderiv-0.0.6:-base4 (conflict:
base==4.7.0.1/installed-e4b..., regex-pderiv-0.0.6:base4 => base<4.0 && >=3.0)
Dependency tree exhaustively searched.