On Wed, Aug 15, 2007 at 03:28:19PM +0100, Duncan Coutts wrote:
We have not reached consensus on this issue yet.
Based on informal chats with interested people, here is another concrete proposal:
Instead of adding isWindows, isBeOS, isNixOS etc we have a simple enumeration of the major OS flavour:
data OSFlavour = Linux | Windows | MacOS | BSD | Solaris | Other String
I really really dislike the 'Other String' thing, it is pretty much always a sign of bad design. Why would some OS's be delegated to 'Other' status just because we happened to not know about them at some point? will all code have to become bloated by saying case os of Linux -> doLinux Other s | s == "Linux" -> doLinux .... or have to use CPP to figure out if other hardcoded values of OSFlavor exist and must be checked for? the data type isn't "normalized" in some sense. there are multiple representations of the same thing, and it arbitrary elevates a few choices to special cases for no good reason. ones that make sense would be either
data OSFlavor = Linux | Windows | MacOS | BSD | Solaris
-- returns OSFlavor if we know it. getOsFlavor :: Maybe OSFlavor
or
newtype OSFlavor = OSFlavor String
However, I don't think either is really needed (but wouldn't hurt) because the practical question we want answered is not whether we are on Solaris or Linux usually, but rather we are on a machine that supports POSIX or if we are on a machine that supports the Win32 API. it is entirely possible to be both (cygwin under windows) for instance. We really should not hard code anything like this in data types. if we want a fast special purpose API (like what was originally proposed) then 'isWindows' is perfect. if we want a general way to query the system type, then a String (perhaps wrapped in a newtype) is the way to go. the halfway approach is the worst of both worlds and just complicates code so, avoid the 'Other'! it will make your code faster, smaller, and more clearly designed and understood. John -- John Meacham - ⑆repetae.net⑆john⑈