Scheme is a functional language in the Lisp family.

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Quick Insert Merge Sort

I have written a code for sorting a list of numbers in increasing order. It is a combination of quick sort, insertion sort and merge sort. I take the first element of the list as Pivot. Then I go ...
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String Matching

I recently came across a lecture on DFA. I tried to use it to determine whether a given 'search string' is found in the 'input string'. Please tell me if there is a better way (display "Enter input ...
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Scheme language questions [closed]

Please can anyone help me with this functions as fast as possible They are in scheme language Write the function extraire_ieme_cartes that retrieves the i-th card of a list of cards given as a ...
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Numeric Value for a Date, dateAdd and dateDiff

In MS excel, a date is also represented as a numeric value, with 1-Jan-1900 as the first day. Also in VBA there are dateAdd and dateDiff functions. dateAdd adds a given unit (day, month quarter or a ...
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Scheme/Racket: idiomatic infix math evaluator

Inspired by xkcd and a couple of praising blog posts, I decided to try out Lisp. It seemed that the best-supported dialect was Racket, itself a variant of Scheme, so I went with that and wrote an ...
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Improving a priority queue sketch in Racket/Scheme

I just put together the skeletons for a priority queue using a binary heap in racket/scheme. Using racket/scheme is all about the educational experience and I was wondering if anyone wants to ...
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A Simple Unix Filter in Racket - Learning the Racket Way

I've written the following simple filter in Racket as my first Racket program and am wondering if I am writing it in an "idiomatic Racket style". #! /usr/bin/env racket #lang racket (require ...
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Counting Ways to Make Change — Is this good functional/Lisp style?

I have just started learning some Scheme this weekend. I recently solved a problem that goes something like: Count the number of ways possible to give out a certain amount of change using 1 5 10 25 ...
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Scheme, first timer first program, simple list removal technique

I have started my hand at writing some scheme code. I am trying to get the first n primes. I plan to do so but first getting a list from 2 to m, and doing the following algorithm. Remove the first ...
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A little scheme programming challenge

I am learning scheme to get something new from a programming language and this code below is the solution to Project Euler question 21 but the code runs 10x slower than the listed Python code when I ...
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Optimize this Scheme-written chess engine module

I'd like to know how to optimize this by shadowing symbols 'lo and 'hi inside nested function f. I guess CPS conversion would solve this but how? ;; chess engine - early development ;; Alist: (cons ...
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Merge sort in Scheme

(define (merge-sort lst (lt? <)) (let sort ((lst lst) (size (length lst)) (flip #f)) (define (merge l r (res '())) (cond ((null? l) (append-reverse r res)) ...
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The Scheme Programming Language Ex 3.4.3

Rewrite the following expression in CPS (Continuation Passing Style) to avoid using call/cc. (define reciprocals (lambda (ls) (call/cc (lambda (k) (map (lambda (x) (if (= ...
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Insert-everywhere

This is HTDP Excercise 12.4.2 :- Page 161 Develop a function insert-everywhere. It consumes a symbol and a list of words. The result is a list of words like its second argument, but with the ...
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SICP ex. 2.42 “eight queens puzzle”

The problem can be found online here. In short, we're given the following function definition, that will recursively generate all the possible solutions for the "eight-queen-problem". (define ...
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Implementing buffered channels in Guile

I was looking for a way of doing simple message passing in Guile and found some references to the module (ice-9 occam-channel) which is a pretty nifty, but undocumented, module for occam-like ...
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A newbie's Program to sort a list in scheme (DrRacket)

Here's a program I wrote to sort a list of numbers in increasing order (without using inbuilt sort function). (define (sort-list l) (define first-element (if (not (null? l)) (car l) 0)) (cond ...
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267 views

An in-nested sequence generator for racket scheme

I've been learning about racket sequences and noticed a hole where nested iteration is concerned. We have the in-parallel construct but no in-nested construct. There's the for*/... family, but ...
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A weblog, implemented in Scheme

It has been said that Lisp - family languages, though not often used to implement web applications, are actually very well-suited to that task, and that all the libraries you need already exist. To ...
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A list builder or list accumulator

Imagine a UTF-8 decoder that takes a list of bytes and returns humman readable code points like: > (utf-8->human-readable-code-points '(32 32 195 160 160)) ("u+0020" "u+0020" "u+00E0" ("Error: ...
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integrating SFML and Box2D lib, and a Mass Production Shape Factory

i just wrote two new headers: one that integrates Box2D and SFML by a class called BodyRep which creates/ is a graphic representation of any body, and one that produces huge amounts of uniform shapes, ...
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Write a procedure stream-limit that finds

From SICP: Exercise 3.64. Write a procedure stream-limit that takes as arguments a stream and a number (the tolerance). It should examine the stream until it finds two successive elements ...
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Write a definition of a semaphore in terms of test-and-set! operations

From SICP: Exercise 3.47. A semaphore (of size n) is a generalization of a mutex. Like a mutex, a semaphore supports acquire and release operations, but it is more general in that up to n ...
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Write a definition of a semaphore in terms of mutexes

From SICP: Exercise 3.47. A semaphore (of size n) is a generalization of a mutex. Like a mutex, a semaphore supports acquire and release operations, but it is more general in that up to n ...
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(Scheme) how to create a function that multiplies all numbers between “a” and “b” with do loop

I'm making a function that multiplies all numbers between an "a" input and a "b" input with do loop. If you please, check my function and say what's wrong since I don't know loops very well in Scheme. ...
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[SICP ex. 3.22] represent a queue as a procedure with local state

From SICP: Exercise 3.22. Instead of representing a queue as a pair of pointers, we can build a queue as a procedure with local state. The local state will consist of pointers to the ...
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SICP ex. 3.18 - Write a program to examine a list for cycles

From SICP: Exercise 3.18. Write a procedure that examines a list and determines whether it contains a cycle, that is, whether a program that tried to find the end of the list by taking ...
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[SICP ex. 3.17] correctly count the number of pairs in an irregular list structure

From SICP: For background, here is exercise 3.16: Exercise 3.16. Ben Bitdiddle decides to write a procedure to count the number of pairs in any list structure. It's easy,'' he reasons.The ...
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[SICP ex. 3.8] order of evaluation of function arguments

From SICP: Exercise 3.8. When we defined the evaluation model in section 1.1.3, we said that the first step in evaluating an expression is to evaluate its subexpressions. But we never ...
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[SICP ex. 2.84] coercion of arguments using successive raising

From SICP: Exercise 2.84. Using the raise operation of exercise 2.83, modify the apply-generic procedure so that it coerces its arguments to have the same type by the method of successive ...
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Find the Hardy–Ramanujan number using R5RS scheme. Please suggest improvements in idiom and calculations.

I remember once going to see [Srinivasa Ramanujan] when he was ill at Putney. I had ridden in taxi cab number 1729 and remarked that the number seemed to me rather a dull one, and that I ...
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(scheme [SICP ex. 2.82] coercion with multiple arguments

From SICP: Exercise 2.82. Show how to generalize apply-generic to handle coercion in the general case of multiple arguments. One strategy is to attempt to coerce all the arguments to the ...
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363 views

Huffman encoding successive-merge function [SICP ex. 2.69]

From SICP: Exercise 2.69. The following procedure takes as its argument a list of symbol-frequency pairs (where no symbol appears in more than one pair) and generates a Huffman encoding ...
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(Encode-symbol …) for Huffman tree [SICP ex. 2.68]

From the text: Exercise 2.68. The encode procedure takes as arguments a message and a tree and produces the list of bits that gives the encoded message. (define (encode message tree) ...
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Lookup (search) on a binary tree [SICP ex. 2.66]

From SICP: Exercise 2.66. Implement the lookup procedure for the case where the set of records is structured as a binary tree, ordered by the numerical values of the keys. I wrote the ...
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Union-set intersection-set for a binary-tree implementation of sets [SICP ex. 2.65]

From SICP: Exercise 2.65. Use the results of exercises 2.63 and 2.64 to give (n) implementations of union-set and intersection-set for sets implemented as (balanced) binary trees.41 I ...
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(scheme) [SICP ex. 2.62] union-set for ordered representation

From SICP: Exercise 2.62. Give a (n) implementation of union-set for sets represented as ordered lists. I wrote this answer: (define (union-set set1 set2) (cond ((null? set1) set2) ...
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(scheme) [SICP ex. 2.61] adjoin-set for an ordered set representation

From SICP: Exercise 2.61. Give an implementation of adjoin-set using the ordered representation. By analogy with element-of-set? show how to take advantage of the ordering to produce a ...
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(scheme) [SICP ex. 2.60] Set representation allowing duplicates

From SICP: Exercise 2.60. We specified that a set would be represented as a list with no duplicates. Now suppose we allow duplicates. For instance, the set {1,2,3} could be represented as ...
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(Scheme) [SICP ex. 2.59] union-set

One way to represent a set is as a list of its elements in which no element appears more than once. The empty set is represented by the empty list. In this representation, element-of-set? ...
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Standard Algebraic Derivative Calculator [SICP ex. 2.58 part b]

I had some difficulty with this problem, so I'm sure there is a better way. Here is the question from SICP: Exercise 2.58. Suppose we want to modify the differentiation program so that it ...
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On Implementing a Lisp

Background: This began with James Colgan's Lisp-Dojo for Ruby. My implementation can be found here. I then moved on to Write yourself a scheme in 48 hours. This question has to do with one of the ...
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(Scheme) [SICP ex. 2.57] Extend sums and products functions without changing deriv function

Exercise 2.57. Extend the differentiation program to handle sums and products of arbitrary numbers of (two or more) terms. Then the last example above could be expressed as (deriv '(* ...
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(Scheme) [SICP ex. 2.56] Extend Differentiator

Exercise 2.56. Show how to extend the basic differentiator to handle more kinds of expressions. For instance, implement the differentiation rule by adding a new clause to the deriv ...
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(Scheme) [SICP ex. 2.54] Define equal?

Exercise 2.54. Two lists are said to be equal? if they contain equal elements arranged in the same order. For example, (equal? '(this is a list) '(this is a list)) is true, but ...
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(scheme) [SICP ex. 2.46] add-vect, sub-vect, scale-vect

Exercise 2.46. A two-dimensional vector v running from the origin to a point can be represented as a pair consisting of an x-coordinate and a y-coordinate. Implement a data abstraction ...
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(Scheme ) [SICP ex. 2.45] Write a general purpose “split” function {for SICP's imaginary language}

From SICP 2.2.4: The textbook has already defined a function (right-split ...) as follows: (define (right-split painter n) (if (= n 0) painter (let ((smaller (right-split painter (- n ...
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(Scheme) [SICP ex. 2.42] eight-queens puzzle - help me fix my popsicle-stick-bridge solution!

Figure 2.8: A solution to the eight-queens puzzle. The ``eight-queens puzzle'' asks how to place eight queens on a chessboard so that no queen is in check from any other (i.e., no two ...
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(Scheme) [SICP ex. 2.41] Find all distinct triples less than N that sum to S

Exercise 2.41. Write a procedure to find all ordered triples of distinct positive integers i, j, and k less than or equal to a given integer n that sum to a given integer s. (define ...
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(Scheme) [SICP ex. 2.40] unique-pairs

From the section called Nested Mappings Exercise 2.40. Define a procedure unique-pairs that, given an integer n, generates the sequence of pairs (i,j) with 1< j< i< n. Use ...

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