[plt-scheme] examining structures, data definitions (ch6 HtDp)

From: Matthias Felleisen (matthias at ccs.neu.edu)
Date: Tue Feb 10 08:21:52 EST 2004

On Tuesday, February 10, 2004, at 03:38 AM, Terrence Brannon wrote:

>  For list-related administrative tasks:
>  http://list.cs.brown.edu/mailman/listinfo/plt-scheme
> I just finished the chapter on compound data and have a few questions:
> (1) how can I examine a structure's components, ie:
> scheme> (inspect posn)
> DOCS: a structure designed to hold cartesian coordinates
> (
>   x
>   y
> )

You "ctrl click" on "posn" and get this in HelpDesk:

Beginning Student Language
posn? in "posn?"
posn-y in "posn-y"
posn-x in "posn-x"
make-posn in "make-posn"

You can then use the hyperlinks to see what they do.

> (2) the chapter said that data definitions were a mix of Scheme and 
> English. Is there no way to create typed structures that require 
> arguments of a certain type?

No. Not yet, I should say.

You should looke at section 7, input errors, if you're a beginner. Or, 
if you have significant experience,
look for module and provide/contract.

-- Matthias

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