Your question wasn’t very specific about what’s being counted. I will presume you want to create some sort of frequency table of the elements. There are several ways to go about this. (If you’re using Racket, scroll down to the bottom for my preferred solution.) Portable, pure-functional, but verbose and slow This approach uses an … Read more
Note: this is cannibalized from an answer to Recursive range in Lisp adds a period?, which is really asking a different question. However, the explanation of how pairs are printed is the same. The rest of the answer is different. Your question exhibits a bit of misunderstanding, but I think we can clear it up. … 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
In this line, you’re calling multBins with (cons 0 x) and (rest y), and getting some result r, and then trying to call r: ((= (first y) 0) ((multBins (cons 0 x) (rest y)))) ; ^ ^ ; +— function application —–+ The same kind of thing is happening in the next line, where you’re … Read more
Are you doing something like this: CL-USER> (defun foo () (let ((value ‘(1))) ; ‘(1) is literal data (incf (car value)))) FOO CL-USER> (foo) 2 CL-USER> (foo) 3 CL-USER> (foo) 4 CL-USER> (foo) 5 Quoted data is literal data; there’s only one copy of it, and the consequences of modifying it are undefined. The behavior … Read more
Why is it happening Scheme procedure/function calls look like this: (operator operand …) Both operator and operands can be variables like test, and + that evaluates to different values. For a procedure call to work it has to be a procedure. From the error message it seems likely that test is not a procedure but … Read more
TL;DR: They are different; use list when in doubt. A rule of thumb: use list whenever you want the arguments to be evaluated; quote “distributes” over its arguments, so ‘(+ 1 2) is like (list ‘+ ‘1 ‘2). You’ll end up with a symbol in your list, not a function. An in-depth look at list … Read more
There are several reasons why one should not use EVAL. The main reason for beginners is: you don’t need it. Example (assuming Common Lisp): EVALuate an expression with different operators: (let ((ops ‘(+ *))) (dolist (op ops) (print (eval (list op 1 2 3))))) That’s better written as: (let ((ops ‘(+ *))) (dolist (op ops) … Read more
A number is even if two divides it evenly, and odd if there if there is a remainder of one. In general, when you divide a number k by a number n, the remainder is one element of the set {0,1,…n-1}. You can generalize your question by asking whether, when k is divided by n, … Read more