Questions tagged [scheme]
Scheme is a functional programming language in the Lisp family, closely modeled on lambda calculus with eager (applicative-order) evaluation.
173
questions
3
votes
0answers
46 views
Performance issue regarding Project Euler #60 in Scheme
I solved Project Euler #60:
The primes 3, 7, 109, and 673, are quite remarkable. By taking any two primes and concatenating them in any order the result will always be prime. For example, taking 7 ...
1
vote
0answers
36 views
Is this zip function ok?
A slick way to write the zip function in Scheme/Racket:
(define (zip . lsts)
(apply map list lsts))
(zip '(a b c) '(1 2 3))
'((a 1) (b 2) (c 3))
Is using cons ...
-1
votes
1answer
48 views
1
vote
1answer
201 views
Implementations of unzip in Racket
I've been practicing my folds and tail-call recursive programming, and I wanted to work on unzip for the general case as opposed to just pairs. This was very easy ...
2
votes
1answer
88 views
Lex Scheme in Rust
I'm writing a Scheme interpreter in Rust, and the first step is the parser. I've finished the lexer, and would like to see what people think of it before I go any further.
...
1
vote
0answers
249 views
Cartesian product in racket (Is append-map okay?)
I've read several places that say it's really bad to use append, and I understand why. I read somewhere that it was never even correct to use ...
2
votes
1answer
47 views
Calculate the sum of the square of two biggest numbers out of three
I'm reading Structure and Interpretation of Computer Programs. In the first exercise, I came across a programming problem to add the squares of the 2 bigger numbers out of 3 numbers.
I came up with ...
2
votes
1answer
195 views
Scheme: FSM substring search
I have been working on a function that return a FSM that searches a specific word based on the argument of the constructor. The idea was to use those routines as means to learn about regular ...
1
vote
0answers
105 views
SICP exercise 3.47 - implementing a semaphore in terms of mutexes
Can anyone check my solution to the first part of exercise 3.47 in SICP? Thanks.
Exercise 3.47: A semaphore (of size n) is a generalization of a mutex.
Like a mutex, a semaphore supports acquire and ...
4
votes
1answer
117 views
RPN calculator in Chicken Scheme
My first attempt at Scheme (Chicken Scheme) - a simple RPN calculator. Please comment on exception handling as well as the general coding style. Here is the code:
...
1
vote
1answer
2k views
Binary search tree insertion in Racket
I am learning Racket and implemented a BST insert function (insert tree n) where the format for a BST node is ...
1
vote
1answer
721 views
Scheme function to duplicate every element of a list a specified number of times
This code takes a list and a integer and duplicates every element in the list the specified number of times.
...
8
votes
1answer
194 views
Peter Norvigs' lis.py in c++17
I wanted to try convert Peter Norvigs' Python Scheme interpreter to C++. I had tried this a few years before and failed abysmally but I saw that the latest C++ standard includes several features ...
4
votes
1answer
93 views
Recamán's Sequence in Racket
I just started learning Racket as my first lisp dialect so after getting used to the syntax I implemented the Recamán's sequence.
Apart from the style, I'd also like to know if my code is a linear ...
3
votes
1answer
57 views
Standalone GNU Makefile tracking `@import` statements in Sass
The following is a (working) excerpt from the Makefile I want to use in web projects. I wanted this Makefile to contain all the necessary code and not rely on other self-written files. Partly, because ...
1
vote
1answer
459 views
Stack calculator in Racket
I have implemented a stack calculator based on this programming task. I wondered if a more experienced racketeer could give me feedback and tell me if I am missing anything in Racket that would enable ...
1
vote
0answers
439 views
Solution to N-queens problem in Racket
I am using following method to solve N-queens problem for all possible solutions for a board. It seems to be smaller as well as faster than many commonly mentioned method. Also, since it is tail-...
1
vote
0answers
162 views
Racket - temperature value converter
I'm giving myself programming challenges in various languages so that I can become a better problem solver i.e. focusing on problem abstraction and algorithm design, using various programming ...
3
votes
2answers
419 views
SICP - exercise 1.7 better end test for square root approximation
Here is exercise 1.7 from SICP:
Exercise 1.7
The good-enough? test used in computing square roots will not be very
effective for finding the square roots ...
1
vote
1answer
144 views
Bash script that creates a local environment for CHICKEN scheme (like virtualenv for Python)
Usage
To create a localenv called sicp, do $ localenv sicp
Activate the localenv: $ . sicp/bin/activate
Check installed eggs in ...
3
votes
0answers
315 views
Knapsack solution in Scheme/Racket
Following is my solution to Knapsack problem using all combinations of the sent list of items (in Racket programming language). Although it is very short, I am sure it can be improved in many ways.
<...
2
votes
1answer
81 views
Structuring flat html structure into a tree
Given an html page with heading tags such h1, h2 through h6 and ...
1
vote
2answers
81 views
Proper use of tail recursion while forming a list
As a project to better develop my understanding of functional programming, I am writing a prime number generator in Scheme. I am using a simple brute-force algorithm to detect whether a number is ...
5
votes
1answer
160 views
Schemey - lexer
1Note: This is the first post in - hopefully - a series of posts I plan to make.
Project background
Schemey is a project I've been working on for the past 3-4 weeks. It is an implementation of a ...
1
vote
0answers
73 views
SICP - exercise 2.5 - Represent pairs of nonnegative integers
Exercise 2.5. Show that we can represent pairs of nonnegative
integers using only numbers and arithmetic operations if we represent
the pair a and ...
1
vote
0answers
117 views
SICP - exercise 2.3 - Implement a representation for rectangles in a plane
Exercise 2.3. Implement a representation for rectangles in a plane. (Hint: You may want to make use of exercise 2.2.) In terms of
your constructors and selectors, create procedures that compute the
...
2
votes
2answers
2k views
Sudoku solver in Racket
I have written following code to solve Sudoku puzzles in Racket (a Scheme/Lisp derivative programming language). Following relatively simple code appears to work but are there any bugs in it or can it ...
2
votes
1answer
245 views
Approximating pi/4 using Wallis Product - SICP exercise 1.31
From SICP
The sum procedure is only the simplest of a vast number of similar
abstractions that can be captured as higher-order procedures. Write an
analagous procedure called product that ...
0
votes
2answers
842 views
Iterative “counting change” implementation in mit-scheme
Here is my iterative implementation of the Counting change example in SICP. Please note that I'm a beginner, which means I only know the basic syntax for the time being.
Requirement:
How many ...
1
vote
2answers
1k views
Pascal's triangle in mit-scheme
As suggested by the name of source file (ex1.12.scm), I just started learning mit-scheme by reading SICP. In Exercise 1.12, I'm asked to "compute elements of Pascal'...
3
votes
1answer
238 views
Simplifying Macro-Generating Racket Macro
I'm trying to write a small macro library in Racket that extends a few of the racket/match functions I use, by printing which clause was expanded.
While this seems ...
3
votes
0answers
217 views
Solving Sudokus in Scheme Using Simulated Annealing
This program's purpose is to solve sudokus using simulated annealing. It first fills all the 3x3 blocks in the sudoku such that every block is filled with 1-9. It also builds a list of pairs of ...
3
votes
0answers
206 views
Converting a sentence string to a number in Scheme
I wrote a scheme procedure that converts strings such as "Two hundred and fifty" into a number like "250" that I can use in math calculations (It's for some Natural Language Processing project).
Is ...
1
vote
2answers
119 views
Function that tests whether all items in a list are the same
The program consists of two functions: the helper predicate function singleton-list? that checks whether a given list contains only one item and the function that ...
2
votes
2answers
5k views
Remove the last occurrence of an item in a list
The objective is given a list of items, remove the last occurrence of a specified item from the list using only user-defined functions except for very basic built-in ones like car, cdr, =, - etc. For ...
3
votes
1answer
411 views
Church Numerals
Here is exercise 2.6 from SICP:
Exercise 2.6: In case representing pairs as procedures wasn’t
mind-boggling enough, consider that, in a language that can manipulate
procedures, we can get by ...
3
votes
1answer
164 views
SICP exercise 1.28 - miller-rabin primality test part II
This is a follow-up to SICP exercise 1.28 - miller-rabin primality test.
Exercise 1.28:
One variant of the Fermat test that cannot be fooled is
called the Miller-Rabin test (Miller 1976; ...
2
votes
1answer
76 views
Find common factor of numbers in a list
This program calculates common factor for given numbers. The original use case is to find a possible resolution for pixel games that scale well with new screen resolutions (that's why I don't have any ...
2
votes
1answer
218 views
SICP exercise 1.28 - miller-rabin primality test
From SICP
Exercise 1.28:
One variant of the Fermat test that cannot be fooled is
called the Miller-Rabin test (Miller 1976; Rabin 1980). This starts
from an alternate form of Fermat’s ...
6
votes
1answer
412 views
Purely functional Sieve of Eratosthenes
Many implementations of Sieve of Eratosthenes (used to find prime numbers up to a given n) use a temporary mutable array to keep track of which numbers are composites. I'm looking to write a purely ...
4
votes
1answer
110 views
SICP 1.3 Sum of Squares of two largest numbers
Define a procedure that takes three numbers as arguments and returns the sum of squares of the two largest numbers.
I'm using just the machinery that was developed so far in SICP to be true to the ...
2
votes
1answer
439 views
SICP - exercise 1.12 - pascal's triangle
From SICP:
Exercise 1.12: The following pattern of numbers is called Pascal’s triangle.
1
1 1
1 2 1
1 3 3 1
1 4 6 4 1
. . .
The numbers at the ...
2
votes
1answer
194 views
SICP - exercise 1.11 - tree recursion
From SICP
Exercise 1.11: A function \$f\$ is defined by the rule that:
\$f(n) = n\$ if \$n < 3\$, and
\$f(n) = f(n-1)+2f(n-2)+3f(n-3)\$ if \$n >= 3\$.
Write a procedure ...
3
votes
1answer
184 views
Square root calculation in Scheme (SICP Exercise 1.7)
I have done exercise 1.7 in SICP (calculate square root precision when change in guesses is under a certain value), but I am calling the change-in-precision function twice in each iteration, which ...
6
votes
1answer
745 views
All possible ways of merging two lists while keeping their order
I am writing a function gives all possible ways of merging two ordered lists such that in the merged list, the elements are still ordered according to the elements in their respective starting list.
...
2
votes
1answer
95 views
SICP exercise 1.3 - sum of squares of two largest of three numbers
From SICP
Exercise 1.3: Define a procedure that takes three numbers as arguments and returns the sum of the squares of the two larger numbers.
Square is:
...
1
vote
1answer
83 views
Functional coffee dispenser [closed]
Inspired by this question, I decided to rewrite this code in Scheme, as I'm working through SICP right now. Any feedback welcome.
...
4
votes
1answer
210 views
SICP - exercise 2.69 - generate a huffman tree from a set of ordered leaves
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 tree ...
2
votes
1answer
112 views
SICP exercise 2.28 - counting leaves in a tree (recursive process)
From SICP
Exercise 2.28: Write a procedure fringe that takes as argument a tree
(represented as a list) and returns a list whose elements are all the
leaves of the tree arranged in left-to-...
2
votes
2answers
297 views
SICP - exercise 2.27 - reversing elements of a list and sublists
From SICP
Exercise 2.27: Modify your deep-reverse procedure of Exercise 2.18 to produce a deep-deep-reverse procedure that takes a list as argument and returns as its value the list with its ...
