[Haskell-cafe] Backpatching

Thomas Conway drtomc at gmail.com
Wed Aug 1 19:00:24 EDT 2007

On 8/2/07, Daniel McAllansmith <dm.maillists at gmail.com> wrote:
> On Wednesday 01 August 2007 17:44, Thomas Conway wrote:
> > This sounds like a common problem type. Is there a well known solution
> > to this sort of problem?
> Have you looked into Tying the Knot?
> http://www.haskell.org/haskellwiki/Tying_the_Knot

I'll need to look further, but I'd say this looks to be on the money.
In many ways it's isomorphic to the logic variable solution (in
Prolog) - it works so long as you don't look at the binding before the
symbol table is complete (i.e. at the end of parsing). Neat. Except
that the Haskell one does not require evil like var/1 to determine
that there are missing bindings. That's pleasing - I knew I walked
away from Prolog for a good reason[*].

[*] It did take a while though - my first Prolog interpreter was
MicroProlog on the Sinclair Spectrum. And that was circa 1980. :-)
Dr Thomas Conway
drtomc at gmail.com

Silence is the perfectest herald of joy:
I were but little happy, if I could say how much.

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