Big sum up of everything:
If TestN is a newtype constructor, then
'TestN undefined' and 'undefined' are exactly the same thing.
2012/1/22 Yitzchak Gale
Is there some litterature expliciting in a less empiric way than I did
Yves Parès wrote: the
differences like this between data and newtype? I've never come against such documentation through all my learning of Haskell, yet I think it's an important point.
Roman Cheplyaka wrote:
See the Haskell report, section 3.17.2 "Informal Semantics of Pattern Matching" [1].
And section 4.2.3 of the report [2] addresses exactly your points very explicitly:
"A type created by newtype differs from an algebraic datatype in that... The following examples clarify the differences between data (algebraic datatypes), type (type synonyms), and newtype (renaming types)..."
Regards, Yitz
[1] http://www.haskell.org/onlinereport/haskell2010/haskellch3.html#x8-600003.17... [2] http://www.haskell.org/onlinereport/haskell2010/haskellch4.html#x10-740004.2...