box% stack install profunctor-optics Error: While constructing the build plan, the following exceptions were encountered: In the dependencies for profunctor-optics-0.0.2: coapplicative must match >=0.0.1 && <0.2, but the stack configuration has no specified version (no package with that name found, perhaps there is a typo in a package's build-depends or an omission from the stack.yaml packages list?) needed since profunctor-optics is a build target. In the dependencies for rings-0.1.3: base-4.9.1.0 from stack configuration does not match >=4.10 && <5.0 (latest matching version is 4.14.0.0) magmas must match >=0.0.1 && <1.0, but the stack configuration has no specified version (latest matching version is 0.0.1) needed due to profunctor-optics-0.0.2 -> rings-0.1.3 Some different approaches to resolving this: * Build requires unattainable version of base. Since base is a part of GHC, you most likely need to use a different GHC version with the matching base. Plan construction failed. box%