I'm using the beginning language with list abbreviations for DrRacket and want to make a powerset recursively but cannot figure out how to do it. I currently have this much (define (powerset aL) ...

I have the following htdp/bsl program saved as example.rkt: #lang htdp/bsl (+ 1 1) When the above is run using racket example.rkt, the output is as expected (i.e. 2). However, when I try to sta...

I just installed DrRacket, and tried out the language "How To Design Programs - Beginning Student". Racket - A programmable programming language Racket - Getting Started I run (+ 1 1), and it ta...

In Exercise 18.1.12 from htdp, I've re-written the maxi function using "local". ;; maxi : non-empty-lon -> number ;; to determine the largest number on alon (define (maxi alon) (cond [(empty...

Or the basic work need to do to create a GUI. I know the basic Components of GUI, but where to begin. I'm just a self-study person and I'm reading "How to Design Program" (HtDP) at the end of the b...

i searched the internet for hours, but didn't find a satisfying answer to what's the difference between the first and second version of HTDP (How to design programs)? Why should I start with...

I am trying to write a source file for DrRacket that specifies one of the languages from How to Design Programs Teaching Languages (see the Racket documentation). I know I can select such a languag...

I want to load an image and animate it in Racket. I can do it easily in the Dr. Racket, but I am using Emacs with Geiser. To load the image I need to: (require racket/draw) Next, to draw this i...

I'm guessing that #lang racket is a dialect of scheme with much more out of the box structures and common functions and perhaps would be more pedagogic. What are the perks a #lang racket against #l...

We have two functions that compute the factorial of a given number. The first one, !, uses an accumulator style. The second, fact, uses natural recursion. (define (! n0) (local (;; accumulator is...