Am Mittwoch, 25. Mai 2005 00:46 schrieb Benjamin Franksen:
On Wednesday 25 May 2005 00:11, Jan-Willem Maessen wrote:
On May 24, 2005, at 5:28 PM, John Meacham wrote:
[various ways of capturing options passed to functions discussed...]
I think it is easier just to declare it as Enum..
data ParentsFlag = DontCreateParents | CreateParents deriving(Enum)
now (toEnum . fromEnum) will convert between ParentsFlag and Bool.
Ah, but imagine I don't have the module source handy. Which corresponds to True and which to False?
Mostly, I stay away from enumerations whose order matters, making a particular exception for Bool and Ord.
If the names are (as above) DontDoSomething | DoSomething, using a newtype plus a boolean conveys the same sense without the forgetfulness:
newtype CreateParents = CreateParents Bool
createDirectory (CreateParents False)
Nice idea. Although this one also introduces additional global names, at least it is syntactically light-weight.
BTW, how about putting all these different ideas on the Haskell wiki?
Ben
What about a type synonym? I think type CreateParents = Bool wouldn't be a bad solution, you can directly use boolean operations and the name makes clear what True and False mean. Daniel