I wrote:
Today, it is very unusual to use GHC by itself. To use Haskell, you install the Haskell Platform. That is GHC together with Cabal and a basic set of libraries. It is very easy to install.
Wolfram Kahl wrote:
However, since you are willing and able to test bleeding-edge versions of GHC, you need to be able to live without the platform, which typically catches up to GHC versions only within a couple of months.
It's true that the platform provides a stable version of GHC, as needed by most people, not the bleeding edge. But even if you need GHC HEAD you would typically use cabal. Unless for some reason you need to shuffle around manually the various pieces that get built, follow trees of package dependencies manually, etc. There are some people who need to do it, and it is doable, though much more complicated and error-prone than just using cabal.
Almost all Haskell software is expected to be installed using Cabal nowadays.
It is important to know that people associate two packages with the name ``Cabal''
They are closely interconnected though. If you use the platform, that distinction is not very important. It just works.
Life without cabal-install is not only possible, but also safer.
I disagree with that. Manual processes are error-prone. With experience, you can learn how to do things totally manually, just like you can learn to build C projects manually without make, and with even more experience, you can learn to avoid all of the pitfalls. It's a good thing to know, but I wouldn't put it at first priority unless there's a special reason for it.
(See also: http://www.vex.net/~trebla/haskell/sicp.xhtml )
The Cabal system is quite mature now, but still far from perfect. Problems can arise. Most of the problems are inherent to the "DLL Hell" that can occur in any separate compilation system, and some arise from the fact that Cabal's dependency solver needs improvement (that's a hard problem). That link is a detailed write-up of just about everything that can possibly go wrong. In my experience, none of that happens until you've been using an installation for a long time, or if you are very trigger-happy with upgrading packages to the latest version for no reason. Or if you're using a package with a huge amount of fast-changing dependencies, like one of the web frameworks. Even then, it's almost always easy enough just to re-install the platform to get a fresh install. Your next few compiles will take a few minutes longer as some packages get rebuilt, but that's about it. To avoid that altogether, I use cabal-dev. This allows me to build a package I am working on in a sandbox with just the dependencies it needs, tailored exactly for the needs of my specific package. Cabal-dev also makes it easy to experiment with how users will experience building my package. It's good to know all the intricacies of the build system, and what is happening beneath the surface if it gets lost. The linked article is a worthwhile read for that. Regards, Yitz