Hi all, Thanks for your comments
Maybe I should clarify... For example, 5.2 FREE: ======== If E1 = \y.xy then x is free If E2 = \z.z then x is not even mentioned So E = E1 E2 = x (\z.z) and x is free as expected So E = E2 E1 = \y.xy and x is free as expected 5.3 BOUND: ========= If E1 = \x.xy then x is bound If E2 = \z.z then is not even mentioned So E = E1 E2 = (\x.xy)(\z.z) = (\z.z)y -- Error: x is not bound but should be by the rule of 5.3 So E = E2 E1 = (\z.z)(\x.xy) = (\x.xy) then x is bound. Where's my mistake in the second-to-last example? Shouldn't x be bound (somewhere/somehow)? Thanks, Mark On 30/12/2010, at 1:52 PM, Mark Spezzano wrote: > Duh, Sorry. Yes, there was a typo > > the second one should read > > If E is a combination E1 E2 then X is bound in E if and only if X is bound in > E1 or is bound in E2. > > Apologies for that oversight! > > Mark > > > On 30/12/2010, at 1:21 PM, Antoine Latter wrote: > >> Was there a typo in your email? Because those two definitions appear >> identical. I could be missing something - I haven't read that book. >> >> Antoine >> >> On Wed, Dec 29, 2010 at 9:05 PM, Mark Spezzano >> <mark.spezz...@chariot.net.au> wrote: >>> Hi, >>> >>> Presently I am going through AJT Davie's text "An Introduction to >>> Functional Programming Systems Using Haskell". >>> >>> On page 84, regarding formal definitions of FREE and BOUND variables he >>> gives Defn 5.2 as >>> >>> The variable X is free in the expression E in the following cases >>> >>> a) <omitted> >>> >>> b) If E is a combination E1 E2 then X is free in E if and only if X is free >>> in E1 or X is free in E2 >>> >>> c) <omitted> >>> >>> Then in Defn 5.3 he states >>> >>> The variable X is bound in the expression E in the following cases >>> >>> a) <omitted> >>> >>> b) If E is a combination E1 E2 then X is free in E if and only if X is free >>> in E1 or X is free in E2. >>> >>> c) <omitted> >>> >>> Now, are these definitions correct? They seem to contradict each >>> other....and they don't make much sense on their own either (try every >>> combination of E1 and E2 for bound and free and you'll see what I mean). If >>> it is correct then please give some examples of E1 and E2 showing exactly >>> why. Personally I think that there's an error in the book. >>> >>> You can see the full text on Google Books (page 84) >>> >>> Thanks for reading! >>> >>> Mark Spezzano >>> >>> >>> _______________________________________________ >>> Haskell-Cafe mailing list >>> Haskell-Cafe@haskell.org >>> http://www.haskell.org/mailman/listinfo/haskell-cafe >>> >> >> _______________________________________________ >> Haskell-Cafe mailing list >> Haskell-Cafe@haskell.org >> http://www.haskell.org/mailman/listinfo/haskell-cafe >> >> > > > _______________________________________________ > Haskell-Cafe mailing list > Haskell-Cafe@haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe > > _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
