Hi,
I'm pretty sure this is not the best mailing list to ask about PLAI, but
as I've found no other I decided to try here (I've found about PLAI on
the original DrScheme mailing list, and racket-lang.org seems to mention
PLAI in the "Learning" section). I won't mind if I don't get an answer
to my question though. Maybe there's a dedicated mailing list?
So, here's my problem, just in case :)
I'm stuck understanding what a certain exercise is asking me. I'm
talking about exercise 8.2.1 from chapter 8, Implementing Laziness.
The exercise asks to implement laziness without using expression
closures, but using thunks instead. Thunks being just like closure,
except they don't have arguments bound to them. What I don't understand
is the fact that this is the way I've implemented expression closures.
They're just like closures, except for the argument part. So, from my
point of view, is just a matter of renaming my algebraic data types.
I'm using Haskell to implement all the languages discussed in the book,
and my ADT for CFAE/L-Value looks like this:
data CFAELValue
= NumberValue Int
| Closure String CFAEL Environment
| Expression CFAEL Environment
deriving (Eq, Show)
So, Expression is the constructor for expression closures, and the only
difference when compared to Closure is the String argument.
Is anyone willing to shed some light on what the exercise does actually
require me to do?
Just for completeness, I've put the Haskell sources for all the
languages up to chapter 8 on Github:
http://github.com/igstan/plai-haskell. CFAE-L.hs is the one used for
chapter 8.
Thanks.
--
Ionuț G. Stan | http://igstan.ro
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