[racket] Simple Scheme Interpreter written in Drracket

From: John Clements (clements at brinckerhoff.org)
Date: Tue Nov 9 15:00:47 EST 2010

On Nov 9, 2010, at 11:48 AM, Peter Breitsprecher wrote:

> I am in the process of writing a simple scheme interpreter for a class I have.  I am running into an issue with regards to parsing the input properly.  I will try and explain what I want to do and tell me if I am way off base or not.  I have a procedure set up to read the input from the user.  Which is just a simple display read function.  I want to pass that read value in, and then read it character by character.  If it is a "(" then up a counter(to make sure there is an equal number of ")", if it is a number, i want to read the number and store it into a variable, and if it is an operator I want to pass the variables to the proper functions I have written to evaluate the input.
> I'm really stuck at step 2...  I can read the input, however I can't seem to pass that input to another function and then break it down character by character.. I thought read-char should do it, but it only seems to work if it is in the function to read the input..  and it doesn't seem to work if passed to another function..

I understand your big picture, but I have no idea what kinds of functions you're trying to write.  Can you describe the function you're trying to write in one line, then specify what it takes and what it returns, and provide a few examples of what you expect it to produce on certain inputs?

In the book "How To Design Programs", these are the first few steps of the "Design Recipe," and it sounds like they would help you clarify what it is you're trying to do.

All the best,

John Clements

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