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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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 2x3. The purpose of this post is to get some feedback; ...
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2answers
36 views

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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1answer
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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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1answer
68 views

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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46 views

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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1answer
37 views

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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2answers
60 views

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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89 views

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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1answer
112 views

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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2answers
168 views

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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1answer
136 views

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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1answer
57 views

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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2answers
179 views

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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57 views

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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1answer
106 views

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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2answers
232 views

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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1answer
96 views

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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1answer
165 views

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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2answers
2k views

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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1answer
152 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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1answer
203 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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1answer
95 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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1answer
141 views

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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161 views

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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1answer
33 views

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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1answer
260 views

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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1answer
132 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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3answers
224 views

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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1answer
84 views

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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2answers
252 views

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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2answers
415 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
104 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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871 views

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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3answers
147 views

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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1answer
149 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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314 views

Tail recursive FizzBuzz in Common Lisp

I solved FizzBuzz using tail recursion. Is it efficient enough? ...
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211 views

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: ...
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1answer
220 views

Unit test macro

I have written a couple of macros (? and ??) for performing unit tests, but I'm having some difficulty with modifying it, so I ...
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2answers
260 views

“Skewed” average in Lisp

I set myself the task to calculate the average of a list, but with two conditions: negative numbers are ignored numbers greater than 100 are counted as if they were 100 So the "skewed" average of ...
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4answers
396 views

Insertion sort in Common Lisp

This is my first bit of significant code in Common Lisp, an implementation of insertion sort. Being new to Lisp in general, I'm wondering if this code follows best Lisp practices in regards to program ...
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2answers
272 views

Standard deviation of hourly temperatures of 2 days

It seems that when I program in Lisp my brain goes on auto pilot and I end up solving the problem somehow. I don't even think I just do and it works out. That said, this is some horrible Lisp code ...
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1answer
61 views

Finding capitalized characters and printing their position & ASCII value

I was trying to find out if a string contained a capitalized letter and if it did I wanted to know the position of the character and its ASCII code. I might have refactored a little to much. Given an ...
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1answer
724 views

Solving the 'Vietnamese school maths problem'

Having read Can you do the maths puzzle for Vietnamese eight-year-olds that has stumped parents and teachers?, which presented the problem of filling in numbers 1 to 9 to satisfy $$ a + 13 \frac{b}{c}...
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1answer
761 views

Functional tree iteration in Common Lisp

I'm adding some functionality to an existing library of data structures in Common Lisp, with a view to asking the original author if I can take over maintenance and development of it. While the ...