Hi, I have a basic question about how output types are reported. I'm using Hugs. Suppose I have the following, where the type String is predefined in the Prelude as [Char]. type PropList = [String] atomicProps1 :: PropList atomicProps1 = ["prop1"] And I have a function on expressions of type PropList which takes every string from the input list and prefixes the string "neg-" to it. negationAtomicProps :: PropList -> PropList negationAtomicProps inPropsList = [ "neg-" ++ inString | inString <- inPropsList] So, with the following, I get the right result:
negationAtomicProps atomicProps1 ["neg-prop1"]
The types for the parts are right:
:t negationAtomicProps negationAtomicProps :: PropList -> PropList
:t atomicProps1 atomicProps1 :: PropList
But, what I don't understand or like is that the type of the whole is given as [[Char]], not what I thought it would be, namely PropList. Nor is it [String].
:t negationAtomicProps atomicProps1 negationAtomicProps atomicProps1 :: [[Char]]
I really want to get the following sort of report for the type: negationAtomicProps atomicProps1 :: PropList The reason I want this is that in more complex cases, it will be easier to see what is going wrong (as the functions are developed) if I can see the types I want. Am I supposed to be using newtype or data declarations here? How would I do this? I looked around for information in the usual sources, but haven't found an answer. Thanks, Adam Wyner