[Haskell-cafe] Re: Wikipedia on first-class object

[Achim Schneider]

"Cristian Baboi" <cristi at ot.onrc.ro> wrote:

> On Mon, 31 Dec 2007 10:59:28 +0200, Achim Schneider <barsoap at web.de>
> wrote:
> 
> > Achim Schneider <barsoap at web.de> wrote:
> >
> >> "Cristian Baboi" <cristi at ot.onrc.ro> wrote:
> >>
> >> > What is infinite in let x = x in x ?
> >>                           ^   |    |
> >>                           |___/    |
> >>                           \________/
> >>
> > a = let x = x in x
> > is actually only quite verbose for
> > a = undefined,
> >
> > the only difference being that undefined is a nicer _|_ than let x
> > = x in x.
> >
> 
> I could have written this instead:
> 
> a :: Something
> a = a
> 
> Which is nicer than undefined.
> 
ksf at solaris ~ % ghci
GHCi, version 6.8.2: http://www.haskell.org/ghc/  :? for help
Loading package base ... linking ... done.
Prelude> let a = undefined
Prelude> a
*** Exception: Prelude.undefined
Prelude> let a = a
Prelude> a
Interrupted.

nope, it isn't.

And then
let a = a
is more defined than the other two... only the equation is _|_, not the
value that is "assigned". Value that is equated? Term? Jonathan, please
beat me.

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