Subject: Re: [CSG111] CSG111: MP4 Extend-Env-Rec?
From: Therapon Skotiniotis (skotthe@ccs.neu.edu)
Date: Mon Feb 27 2006 - 12:38:22 EST
On Sun, Feb 26, 2006 at 09:29:21PM -0500, Wendy wrote:
> Hi,
>
> In the assignment, it asks for the test cases from mp3 to be run. However,
> we are missing a bit f functionality. There was already an email saying we
> don't have to worry about all-of, cond, and, or, not. But what about
> addition, mutliplication, and integer divsion? I'm assuming these should not
> be implemented either. So, should we just exclude all test cases for these?
Yes.
>
> Also, I'm having a lot of trouble with letrec. I have no idea how to make
> recursion happen. The examples from lecture three are building a data
> structure, and this method makes sense. But I am just not seeing how this
> can be done with a list. My code is currently dying after the first run of
> the procedure. The issue is that the environment is storing the value of the
> first run of the procedure, and then nothing else.
You are almost there :)
As you said, when you are evaluating the procedure created
by a letrec, the environment does not have a binding for
this procedure. So you have to differentiate between
procedures created by letrec and evaluate them in the
"right" environment.
-- Theo
> I guess the issue I have
> is I dont see how to take the closure. When you said closure in your email,
> were you talking about the "closure" function in the notes? At this point
> any help would be great as I am definitly not understanding this.
Yes, by closure I mean the same thing as in the lecture
notes.
-- Theo
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