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: singular-factory-0.1 (user goal)
[__1] rejecting: singular-factory:+pkg-cfg-prefix (conflict: pkg-config
package singular-factory-any, not found in the pkg-config database)
[__1] rejecting: singular-factory:-pkg-cfg-prefix (conflict: pkg-config
package factory-any, not found in the pkg-config database)
[__1] fail (backjumping, conflict set: singular-factory,
singular-factory:pkg-cfg-prefix)
After searching the rest of the dependency tree exhaustively, these were the
goals I've had most trouble fulfilling: singular-factory,
singular-factory:pkg-cfg-prefix