If you want to clear the screen, the “ANSI” sequence in a printf \033[2J clears the entire screen, e.g., printf ‘\033[2J’ The command-line clear program uses this, along with moving the cursor to the “home” position, again an “ANSI” sequence: \033[H The program gets the information from the terminal database. For example, for TERM=vt100, it … Read more
I recently fixed this bug in Guile 2.0. The bug came into existence when C compilers started optimizing out overflow checks, on the theory that if a signed integer overflow occurs then the behavior is unspecified and thus the compiler can do whatever it likes.
Great question. For the benefit of those without a functioning DrRacket installation (myself included) I’ll try to answer it. First, let’s use some sane (short) variable names, easily trackable by a human eye/mind: ((lambda (h) ; A. (h h)) ; apply h to h (lambda (g) (lambda (lst) (if (null? lst) 0 (add1 ((g g) … Read more
It strikes me you’d rather see it from the horse’s mouth, so here’s a choice extract from a message Rich posted: Scheme #t is almost completely meaningless, as Scheme conditionals test for #f/non-#f, not #f/#t. I don’t think the value #f has much utility whatsoever, and basing conditionals on it means writing a lot of … Read more
The new Racket language (formerly PLT Scheme) allows you to implement any semantics you like with s-expressions (really any syntax). The base language is an eagerly evaluated, dynamically typed scheme variant but some notable languages built on top are a lazy scheme and a functional reactive system called Father Time. An easy way to make … Read more
Use Racket (formerly PLT Scheme). The DrRacket IDE is an excellent starting point for all things Scheme including SICP. To look up keywords in the documentation, place the cursor on the keyword and press F1. In DrRacket you can now see the images directly in the REPL (the read-eval-print-loop). SICP Support for DrRacket, by Neil … Read more
Clojure is an actively developed, modern dialect of Lisp. It’s based on the JVM, so all the Java libraries are immediately available, and therefore also has Unicode support. This is one alternative, not the One True Answer.
Try something simpler to see how this works. For example, here’s a version of a list-sum function that receives a continuation argument (which is often called k): (define (list-sum l k) (if (null? l) ??? (list-sum (cdr l) ???))) The basic pattern is there, and the missing parts are where the interesting things happen. The … Read more
SLIME’s contrib directory seems to have SWANK implementations for MIT Scheme and Kawa.
It means that your program code you write is also data which can be manipulated by a program. Take a simple Scheme expression like (+ 3 (* 6 7)) You can regard it as a mathematical expression which when evaluated yields a value. But it is also a list containing three elements, namely +, 3 … Read more