4h - Detection of the current status of operating system

[freeman42x]

Write functions that do the bellow:

• is GHC installed? isGhcInstalled
• is cabal installed? isCabalInstalled
• is stack installed? isStackInstalled etc.
• is Nix installed? isNixInstalled
• which Nix configuration files are being used: /etc/nixos/configuration.nix, user level config, etc. (create ADT for the file being used:

Research what are all the possible ways to configure Nix globally per user and then add them to NixConfiguration:

data NixConfiguration = System | UserLevel | Custom
getExistingNixConfigurations = [NixConfiguration]