Understanding Scheme I think at least half of the problem with understanding this puzzle is the Scheme syntax, which most are not familiar with. First of all, I personally find the call/cc x to be harder to comprehend than the equivalent alternative, x get/cc. It still calls x, passing it the current continuation, but somehow … Read more
From R5RS Standard Pocedures: (expt z1 z2) Returns z1 raised to the power z2. For z1 0 z1z2 = ez2 log z1 0z is 1 if z = 0 and 0 otherwise. Searching for “scheme reference” turns up this document.
All three of the forms you mention are single-line comments. The double-semicolon may have originally arisen as a cue in Dorai Sitaram’s SLaTeX typesetting package that the comment was to be typeset as ordinary text, rather than as program text. Scheme also has multi-line comments. In particular, it appears that R6RS, like Racket, allows the … Read more
current-milliseconds is a function that returns the current millisecond count from the system, but it might decrease. current-inexact-milliseconds is similar, but returns a guaranteed-to-increase floating point number. There are also a bunch of similar functions that you can find on that page, but if all you need is to time a certain function, then just … Read more
Natively compiled Lisp systems are usually quite a bit faster than non-natively compiled Lisp, Ruby or Python implementations. Definitions: natively compiled -> compiles to machine code compiled -> compiles to machine code or some other target (like byte code, JVM instructions, C code, …) interpreted Lisp -> runs s-expressions directly without compilation interpreted Python -> … Read more
Other answers have given all the good choices, but without much description. Here’s some more detail: DrRacket Racket’s IDE, DrRacket, is a great tool for beginners and has a lot of strengths for more advanced schemers. It has good profiler and debugger support (far better than Emacs), uses “standard” keyboard shortcuts by default, and is … Read more
In DrRacket there is a SICP compatibility language 1. From the Package Manager In the documentation there is an easy guide to how it’s installed from DrRacket: Open the Package Manager: in DrRacket choose the menu “File” then choose “Package Manager…”. In the tab “Do What I Mean” find the text field and enter: “sicp” … Read more
What is a prompt, conceptually? Scheme in general has the idea of continuations, but Racket extends this with the idea of delimited continuations. The idea of a continuation is that it captures the remaining computation left to be evaluated. I will not attempt to explain continuations in general, since that is outside the scope of … Read more
You need to capture the state in some accumulators and update the state at each iteration. If you have experience in an imperative language, imagine writing a while loop and tracking information in variables during each iteration of the loop. What variables would you need? How would you update them? That’s exactly what you have … Read more
DrScheme is the best Scheme IDE I have found. It has a JIT compiler, can build stand-alone executables or run in the traditional Scheme REPL, has smart syntax editing , as well as other traditional IDE features like Menu bars to change features. Running/stopping your program is as easy as clicking ‘Run”https://stackoverflow.com/”Stop’. It also includes … Read more