On Fri, May 14, 2010 at 12:08 PM, Nobody <nob...@nowhere.com> wrote: > On Tue, 11 May 2010 18:31:03 -0700, Paul Rubin wrote: >>>> is called an "equation" rather than an "assignment". It declares "x is >>>> equal to 3", rather than directing x to be set to 3. If someplace else >>>> in the program you say "x = 4", that is an error, normally caught by >>>> the compiler, since x cannot be equal to both 3 and 4. >>> >>> In both ML and Haskell, bindings are explicitly scoped, i.e. >>> let x = 3 in ... (Haskell) >> >> I'm not talking about nested bindings. I'm talking about two different >> bindings of the same symbol in the same scope: >> >> $ cat meow.hs >> x = 3 >> x = 4 >> $ ghc meow.hs >> >> meow.hs:2:0: >> Multiple declarations of `Main.x' >> Declared at: meow.hs:1:0 >> meow.hs:2:0 > > It may be worth noting the interactive behaviour: > > $ ghci > GHCi, version 6.8.2: http://www.haskell.org/ghc/ :? for help > Loading package base ... linking ... done. > Prelude> let x = 7 > Prelude> let f y = x + y > Prelude> f 3 > 10 > Prelude> let x = 5 > Prelude> f 3 > 10
Ahem (emphasis mine): """ ==This syntax is *ghci-specific*== The syntax for 'let' that ghci accepts is not the same as we would use at the “top level” of a normal Haskell program. """ -- http://book.realworldhaskell.org/read/getting-started.html Cheers, Chris -- http://blog.rebertia.com -- http://mail.python.org/mailman/listinfo/python-list
