Questions tagged [common-lisp]

Common Lisp, or ANSI Common Lisp, is a standardized version of the Lisp programming language intended for production-strength power and libraries.

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Generating HTML for prerolled d20 RPG initiative tables

A fairly simple program that I tried to write in Common Lisp in order to practice/learn. I'm sure this can be done more elegantly but Lisp's string handling seems to be very werd. ...
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BST traverse as higher order function [closed]

Consider the following function to traverse a BST ...
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1answer
43 views

Abstracting on Common Lisp Function Keyword Parameters

This is an experiment on extending a basic built-in Common Lisp sequence function (namely remove), in order to provide more functionality with little or no impact ...
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Find minimum value in a BST: using boolean operators, and using conditionals

I've been studying the BST code in Paul Graham's ANSI Common Lisp. He provides (my comments): ...
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Count frequencies of symbols in a list

I'd like to find a more elegant solution to the following. Below appears correct, but it's hard to read. Is my first use of the map function below poor in stylistic terms? It feels that way, and ...
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Sum ints on stdin

I have been meaning to learn LISP and for a small task I wanted to find out the sum of all integers on STDIN. So for > clisp a.lisp 1 2 3^D 6 My code is as ...
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Uncompressing a list with some run-length-encoded elements

Regarding the following code ...
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52 views

Evaluator for adding and subtracting algebraic expressions

I wrote a little program that adds and subtracts some algebraic expressions. In my code (2 x 3) represents \$2x^3\$. The purpose of this post is to get some ...
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Generating a list (or a string) with random elements

During implementation and testing of different small hobby projects I often reach the point where I need (at least I like it more) some random data beyond the usual foo-bar strings or lists. Random ...
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Calculating the cube root

Inspired by a question on SO I was checking how to calculate the cube root of an integer and found a C-ish solution on Hacker's Delight: ...
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merge function for mergesort - recursion vs. iteration

I decided to do an algorithms course (Roughgarden's on Coursera), and am setting out to implement each algorithm as it's introduced, in Lisp. We start with mergesort which is introduced as the ...
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Binary Heap implementation in Common Lisp and tests

I implemented a basic [binary heap] https://en.wikipedia.org/wiki/Binary_heap() in Common Lisp to learn programming using the CLOS. It is quite neat and self-contained, the core of the program is ...
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41 views

Utmost function that takes a comparator function

I'm working through Paul Graham's "ANSI Common Lisp". In Chapter 6 (p105), he introduces the idea of utility functions. He points out these are core to bottom-up programming and reusability. He ...
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Nested loop in lisp to process a 2d array - what's good style (with and/or without loop macro)? [closed]

Code below is answer to an exercise in Paul Graham's ANSI Common Lisp (ex. 4.1). The challenge is to rotate an array by 90 degrees. I found an example solution which I've commented below. It seems ok'...
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Puzzling SBCL Compiler Note

I’m having trouble understanding an SBCL compiler note about unreachable code in the following function. The referenced code is attempting to push a value into an Lparallel queue: ...
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A Parallel Processing Template for Divide & Conquer Problems

I’ve written a program for solving a problem using standard single-threaded code. However, it looks like it could be recast as a multi-threaded problem using divide & conquer. Since this is a ...
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Enigma questions from “ANSI Common Lisp” [closed]

I'm working through Paul Graham's ANSI Common Lisp and in Exercise 2.5, I'm stumped. My specific question (I wasn't sure whether this type of question is suitable for stack overflow, code review, or ...
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pos+ (value added to position) - ex 3.5 in “ANSI Common Lisp” (p57)

The problem is to take a list of integers and map them to another list containing those integers added to their respective position in the list. Example runs with required outputs: ...
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Occurrences (frequency count) - exercise 3 ch. 3 in “ansi common lisp”

Looking for hints on style and clarity re. below. While I'm not saying speed is irrelevant, it's less of a priority than style & avoiding bad habits at this point. Focus is on clean use of ...
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Verify that each named sequence is strictly increasing

The master launch sequence consists of several independent sequences for different systems. Your goal is to verify that all the individual system sequences are in strictly increasing order. In other ...
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Implementing a tree parsing function

I've solved an assignment a week ago, which is my first assignment using Lisp. Tasks: Task 1: a. Given a tree as recursive lists, print the tree in breadth first order. b. Given a tree like ...
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A simple Tic Tac Toe game

I am trying to learn some Common Lisp, except basically all of my computing background is the C family of languages. So, I'm starting small. I have made a Tic-Tac-Toe game, and I am looking for some ...
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FizzBuzz in Common Lisp

Where I stand on Lisp So, Lisp. It's been on my radar for years and I'm finally getting around to learning it. The syntax is foreign but I find I'm having the most difficulty in the areas of ...
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Extracting XML data from a node in Common Lisp (Closure XML DOM)

This is a function intended to take an XML element (in closure XML format) and a name and find a piece of simple data by that name (either in a tag or attribute) within that XML element. It works, but ...
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Returning the prime factors of a number

I am trying to create a function prime-factors that returns the prime factors of a number. To do so, I created is-prime function,...
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Pure functional code for the sublists of a list

The code below gives me the list of sublists of a list. Code can still be improved to avoid the use of append, right? ...
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lisp-koans Greed implementation

I have implemented Greed as part of the lisp-koans extra-credit challenge. I am seeking some general feedback with respect to Common Lisp style, appropriate use of language features, and so forth. ...
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Reading lines of integers into a list of lists

I have a text file containing integers in different lines which I want to read into a list of lists. So 01 11 14 45 50 09 should become ...
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Calculating insulin bolus dose and infusion rate

I wrote a hobby program to ease the job of nurses to calculate insulin bolus dose and infusion rate according to measured blood glucose. There are several protocols around. Almost all hospitals ...
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Scoring poker hands

Just for fun I solved another Project Euler problem dealing with poker cards. I think it is also part of other programming puzzles which can be found in the web. While there is not much mathematics in ...
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Split a list into two parts with a given length

I'm learning Common Lisp as a hobby and am trying tasks from L-99: Ninety-Nine Lisp Problems, but I'm not sure how good my code is. Here is one of the tasks which I solved: GitHub solution ...
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168 views

Pairwise grouping of elements of a list

I want to group the elements in an arbitrary long list into pairs and implemented the following so far: ...
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211 views

(SBCL) ASCII Game of Life

I'm implementing Conway's Game of Life in Lisp to familiarize myself with the language, with the eventual goal of hosting it on a website with a pretty GUI. I'm a hobbyist and inexperienced (this is ...
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101 views

Calculation of lexicographic permutations

Just for fun, I studied the generation of lexicographic permutations and came across the following algorithm which I transcribed into Common Lisp, as good as I can, being a hobbyist: ...
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Extending COERCE to other reasonable object type conversions

It's a basic principle in AI that different problem representations can either facilitate or impede a solution. Being able to readily switch data representations while programming in Common Lisp may ...
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Language training program using Common Lisp and the ltk library

The idea is as follows: We provide program with two files: one with English words and one with words in, let's say, Spanish. The files have one word (it could be a word, or word+some explanation etc) ...
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Determine indentation of a line of code

The following function determines the amount of indentation of a string. It returns two values. The first is an effective indentation where tabs are expanded such that their end aligns with 4 spaces ...
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Generic copy function

Common Lisp does not have a generic copy function for reasons outlined in Kent Pitman's article The Best of Intentions. However, it may still be convenient for rapid prototyping purposes to provide ...
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134 views

Using get-setf-expansion

In a previous post at Simplifying complex setf expressions, @sds suggested using the get-setf-expansion macro for implementing place modification, as discussed in ...
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Invert the bits of a non-negative integer in Common Lisp (SBCL)

I'm doing code challenges to learn Common Lisp. I'm trying to invert all the bits in any given positive integer. My current solution does it the math way, by recursing on a number, dividing it by two,...
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A heart.lisp I wrote with my 6 year old daughter

Is it possible to improve this program somehow? It will probably be more convenient to suggest edits as forks of this Gist. ...
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Project Euler #2 (classic) - Sum of even fibonacci numbers below 4 million

I'm looking to use LISP as best I can, not just get the right answer. This is very early on in my LISP career so feedback is welcome and exciting! Recently asked about Project Euler #1, got some ...
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421 views

Sum of all multiples of 3 or 5 below 1000 (Project Euler #1 - typical)

I'm learning LISP and am starting with Project Euler. I would love some initial feedback on my LISP code for this simple task. I know it spits out the correct answer, but what I'm not sure about is ...
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1answer
108 views

Sort 3 numbers in Common Lisp with the minimum number of operations

I’m wondering is the following function returns a list of three numbers sorted in ascending order with the minimum possible number of operations, or if there is some more efficient or elegant method (...
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A Lisp version of the Schwartzian transform

Randal Schwartz stole Lisp's decorate-sort-undecorate idiom when he came up with what we'd later call the Schwartzian transform. All of my Lisp knowledge disappeared through nine half lives, but I ...
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Netstring parser in common lisp

Below is a netstring parser I wrote in Common Lisp. The docstring contains the usage and return. ...
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153 views

Once-only macro

I have been learning common lisp and am a newbie, using the great book Practical Common Lisp. There is a once-only macro in the book that I spent a lot of time figuring out how it works. Even after I ...
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322 views

Tail recursive FizzBuzz in Common Lisp

I solved FizzBuzz using tail recursion. Is it efficient enough? ...
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Advent of Code: “Not Quite Lisp”

I have solved this simple challenge on Advent of Code: Santa is trying to deliver presents in a large apartment building, but he can't find the right floor - the directions he got are a little ...
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1answer
92 views

Golden Section Search in Lisp

I implemented the golden section search algorithm recursively in Lisp. My code is: ...