Scheme is a functional programming language in the Lisp family, closely modeled on lambda calculus with eager (applicative-order) evaluation.

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Solving the N-queens puzzle the Racket or Scheme way

My final version is a direct translation from Python. Thanks to build-in support for generator, its speed is almost the same as Python. As I quite like using generator and list comprehension in ...
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2answers
45 views

Is there a better way to document this or is this good enough?

I finished answering Exercise 3.3.1 of How to Design Programs where: Exercise 3.3.1. The United States uses the English system of (length) measurements. The rest of the world uses the metric ...
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Is my implementation of a merge sort correct?

I tried to get into programming several times but never did and never got very far past "Hello, World.", until recently when I found and read (most of, still don't get parts of it) "The Little ...
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98 views

Code from “Write Yourself a Scheme in 48 Hours” tutorial

I recently went through this Haskell tutorial. I'd be interested in any thoughts or comments at all, in terms of improving the structure, order, haskell conventions, or that long, kind of ugly eval ...
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63 views

This snippet of scheme calculates a value in pascal's triangle

I'm working through SICP and have implemented exercise 1.11 (Pascal's Triangle). What I'm curious about here is performance considerations by defining functions within the main function. I would ...
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120 views

Rosalind's 3rd problem in Scheme

I have an imperative programming background and I've decided to study functional programming by applying it to problems found on sites such as Project Euler and Rosalind. My language of choice is ...
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359 views

My first accumulators

Notes I'm working my way through SICP, and as I got very confused by the section on folds, I decided to try to implement foldr in scheme and javascript to understand how it works differently with ...
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4answers
126 views

Project Euler 1 (sum of multiples of 3 or 5 under 1000)

I solved this a while ago. In the moment I solved it I was learning Scheme and, well, I still am. I'm not looking at the best solution (I searched for it and coded it already, in Python), what I want ...
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20 views

Completing a Graph in Scheme

For the record, this is part of a homework assignment, but I have already implemented a solution. I am simply wondering if there is a better way to do it. Background: I am asked to write a procedure, ...
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57 views

lexical scope v let in scheme functions

I've been chewing through a bit of The Little Schemer and the Peano examples got me thinking about operation size and time. I got some help on making Peano Multiplication linear -- however ...
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1answer
41 views

Linear Peano multiplication in Scheme?

I've been running through The Little Schemer, and have hit the example of Peano multiplication. The solution is given in TLS (reproduced below) -- however what interests me is the order of the ...
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1answer
138 views

remove first occurance of element from list

As explained here i'm learning a limited subset of scheme. My task has been to sort a numerical list. To implement a simple insertion sort, i need to remove a single element from a list. I've ...
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352 views

sorting a numerical list using basic scheme

I would like some feedback on the appropriate way of ordering a numerical list using the most elementary scheme functions (sorry, i realise that elementary is not ...
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228 views

Why is this RC4 code in Racket so slow?

According to shootout.alioth.debian.org, Racket is not much slower than C#, at least in the same order of magnitude due to its JIT compiler. However, I'm seeing at least two degrees of magnitude ...
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68 views

Creating an updating hash table

I'm not sure if this implementation is good enough. The function takes a vector of 1 million chars and creates a table of the sequences that pass before the next occurrence of itself. Some questions ...
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25 views

A with-input-from-pipe for Guile

I wrote this with-input-from-pipe function for Guile. I’m not that comfortable with dynamic-wind or ...
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0answers
53 views

`multiple-value-call` in Scheme

Common Lisp has a "special operator" called multiple-value-call, which does something similar to Scheme's call-with-values but ...
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37 views

Check if element is a member of all sets in Scheme

Here is a function that checks whether an alement a is a member of every set in list l-set. I don't like the fact that it ...
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101 views

Quick Insert Merge Sort

I have written this code to sort a list of numbers, in increasing order. It is a combination of quick sort, insertion sort, and merge sort. I make the first element of the list a pivot, then I go ...
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40 views

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 ...
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1answer
126 views

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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1answer
241 views

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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1answer
272 views

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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1answer
191 views

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". ...
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2answers
408 views

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: ...
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1answer
252 views

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 ...
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2answers
306 views

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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1answer
120 views

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? ...
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583 views

Merge sort in Scheme

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421 views

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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138 views

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". ...
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75 views

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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2answers
3k views

Sorting a list of numbers in increasing order

Here's a program I wrote to sort a list of numbers in increasing order (without using inbuilt sort function). ...
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1answer
451 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 ...
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1answer
486 views

A list builder or list accumulator

Imagine a UTF-8 decoder that takes a list of bytes and returns humman readable code points like: ...
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2answers
160 views

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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145 views

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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147 views

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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1answer
104 views

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 ...
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118 views

Representing 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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1answer
192 views

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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275 views

[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. ...
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1answer
210 views

[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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1answer
433 views

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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298 views

(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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1answer
557 views

Huffman encoding successive-merge function

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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1answer
602 views

Encode-symbol for Huffman tree

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. ...
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1answer
286 views

Search on a binary tree

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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770 views

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 ...