Lisp is a (family of) general purpose programming language(s), based on the lambda calculus, and with the ability to manipulate source code as a data structure.
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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
...
3
votes
2answers
65 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,...
3
votes
1answer
37 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.
...
4
votes
2answers
63 views
Definition of power functions
I needed to write a simple function that could raise a value x to the n'th power. I found out I could write this function in 2 ...
8
votes
2answers
74 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 ...
4
votes
2answers
168 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 ...
3
votes
0answers
41 views
Computing nth roots of a number - SICP exercise 1.45
From SICP
Exercise 1.45:
We saw in 1.3.3 that attempting to compute square roots
by naively finding a fixed point of x/y does not converge, and that
this can be fixed by average damping.
...
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1answer
48 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 ...
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2answers
51 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'...
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votes
2answers
42 views
Highest number in a list with Racket
I am trying to build a function to find the highest number in a list without using the built-in functions of "apply" and "max".
I created the following code:
...
3
votes
2answers
45 views
GUI implementation with Racket
I am studying the book Realm of Racket.
On chapter 5, there is a challenge:
Find an image of a locomotive. Create an animation that runs the locomotive
from just past the left margin to just past ...
3
votes
0answers
26 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 ...
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2answers
67 views
Reverse the order of a list in Racket
I am using the SICP book. There is an exercise in which you need to create a function that will receive a list as an argument and return a list with the same elements in a reverse order.
I know there ...
5
votes
1answer
46 views
“Guess My Number” with Racket
I am using the book "Realm of Racket" which was written by the people behind the Racket and Dr. Racket projects. It is a great book based on games, similar to the famous "Land of Lisp".
The first ...
3
votes
1answer
75 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
97 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; ...
6
votes
1answer
40 views
PE4: Largest Palindrome Product (Clojure)
I solved Project Euler 4 using Clojure Lisp.
A palindromic number reads the same both ways. The largest palindrome made from the product of two 2-digit numbers is 9009 = 91 × 99.
Find the largest ...
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votes
2answers
753 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. With all of my LISP knowledge disappeared through nine half lives, but ...
2
votes
1answer
35 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 ...
3
votes
2answers
67 views
Netstring parser in common lisp
Below is a netstring parser I wrote in Common Lisp. The docstring contains the usage and return.
...
1
vote
1answer
90 views
Exercism: clean and format a phone number in Clojure
Problem statement
Phone Number
Write a program that cleans up user-entered phone numbers so that they can be sent SMS messages.
The rules are as follows:
If the phone number is ...
2
votes
1answer
115 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 ...
5
votes
1answer
69 views
Selecting HTML nodes
I'm new to Clojure, and I'm writing some code that processes HTML. I'm parsing the HTML using clj-tagsoup and then trying to pull out the relevant bits with this function:
...
2
votes
1answer
29 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 ...
1
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1answer
52 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 ...
3
votes
2answers
158 views
Tail recursive FizzBuzz in Common Lisp
I solved FizzBuzz using tail recursion. Is it efficient enough?
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8
votes
1answer
190 views
“Curious Numbers” (HackerRank PE 34)
I was inspired by a certain recent question to try my hand at this challenge:
Project Euler #34: Digit factorials
\$19!\$ is a curious number, as \$1!+9!=1+362880=362881\$ is divisible
by \$19\$...
3
votes
1answer
60 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 ...
8
votes
2answers
98 views
Compiler for a minimal LISP dialect to run on the Java Virtual Machine
As the title states, this is a compiler written in C with a ruby build script that translates a minimal LISP dialect and spits out an executable jar file. I designed this LISP dialect and named it ...
2
votes
1answer
54 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:
...
2
votes
1answer
168 views
Mutable stack in Racket
I'm learning Racket and have implemented a mutable stack, which is just a bunch of wrappers around an underlying struct containing a size and buffer list (so it's ...
3
votes
1answer
59 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
79 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 ...
2
votes
1answer
54 views
SICP - exercise 2.5 - representing pairs of nonnegative integers using only numbers and arithmetic operations
From SICP
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 b as the integer that is the product 2^x*3^...
2
votes
1answer
25 views
Replacing elements from a list and its sublists - part II
This is sort of a follow-up to
Replacing elements from a list and its sublists
but now there are arbitrary numbers of words that would be replaced stored in a list.
Now write substitute2 that takes ...
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2answers
48 views
SICP - exercise 2.20 - same-parity
Exercise 2.20.
The procedures +, *, and list take arbitrary numbers of arguments. One way to define such procedures is to use define with dotted-tail notation. In a procedure
definition, a parameter ...
3
votes
1answer
90 views
Reversing a list without (append)
I would like to reverse a list using cdr, car and cons. Since lists in lisp are asymmetrical (can only insert at the beginning), I am interested on how one would write a procedure to do that without ...
3
votes
1answer
60 views
Replacing elements from a list and its sublists
Write a procedure substitute that takes three arguments: a list, an old word, and a new word. It should return a copy of the list, but with every occurrence of the old word replaced by the new word, ...
11
votes
2answers
131 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
...
5
votes
1answer
89 views
Finding next perfect number - brute force
A “perfect number” is defined as a number equal to the sum of all its factors less than itself. For example, the first perfect number is 6, because its factors are 1, 2, 3, and 6, and 1+2+3=6. The ...
3
votes
1answer
58 views
Replacing words from a sentence
I am extremely new at scheme and I am doing this problem from here:
Write a procedure switch that takes a sentence as its argument and
returns a sentence in which every instance of the words I or ...
2
votes
1answer
74 views
Golden Section Search in Lisp
I implemented the golden section search algorithm recursively in Lisp. My code is:
...
6
votes
1answer
106 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 ...
2
votes
2answers
150 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 ...
3
votes
2answers
104 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 ...
1
vote
2answers
129 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 ...
6
votes
1answer
350 views
Binero puzzle solver
During my holiday I decided to implement a solver for those puzzles my girlfriend likes to do. They are called Takuzu, but "binero" in Dutch.
The puzzle gives you a grid in which you have to fill in ...
7
votes
1answer
227 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 ...
2
votes
1answer
507 views
Simple, functional URL parsing library in Clojure
I recently wrote some code to handle parsing of URLs, even if those URLs might not be one hundred percent perfectly well-formed. (This constraint made using Java's ...
5
votes
1answer
516 views
ANFIS network based on Sugeno model I
I've been learning Common Lisp lately and I've implemented ANFIS network based on Sugeno model I.
Network layout and details can be read in these slides by Adriano Oliveira Cruz.
I use sigmoid as the ...
