Re: [Haskell-cafe] newtype and access control

Hi Brandon, I think that exporting the data constructor was a simple oversight. I can definitely see how, if you don't export the data constructors, other modules can't pattern match on the newtype value and therefore can't "get at" the WithDBConn a value. Thank you! On Oct 29, 2017 7:58 PM, "Brandon Allbery" wrote:

On Sun, Oct 29, 2017 at 7:52 PM, Steven Leiva wrote:

...

Out of necessity, the speaker has to assume a certain level of Haskell knowledge that I don't have, because I am confused as to what language principles would allow for *inDBTrans* to be used for access control.

As presented, that doesn't seem to be true. If the module exported only the type constructor, then it would be impossible for other modules to pattern match it and access the wrapped value. But the module has no export list, so it exports everything including the data constructor and modules can pattern match to unwrap it; the only other way to get that kind of isolation is for the wrapped data type to not be in scope, but that also doesn't seem to be the case.

-- brandon s allbery kf8nh sine nomine associates allbery.b@gmail.com ballbery@sinenomine.net unix, openafs, kerberos, infrastructure, xmonad http://sinenomine.net