Sandbox for Proposed Challenges

Question

This "sandbox" is a place where Code Golf users can get feedback on prospective challenges they wish to post to main. This is useful because writing a clear and fully specified challenge on your first try can be difficult, and there is a much better chance of your challenge being well received if you post it in the sandbox first.

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Answer 1

Tag: code-golf

Arrays

I originally wrote it in Chinese and am still working on translating it. Sorry for the inconvenience.

Given an array containing n integers A1,A2,…,An, where all of their initial values are 0. Please implement the four operations to the array described below:

Operations

Given the positive integer x and y, let every number in the range Ax~Ay (including Ax and Ay) be added by the given positive integer c;
Given the positive integer x and y, let every number in the range Ax~Ay be (similarly to the previous spec; the rest of the spec also conforms that rule) multiplied by a given positive integer c;
Given the positive integer x and y, let every number in the range Ax~Ay be changed to a given positive integer c;
Given the positive integer x and y, with regard to a given positive integer p, evaluate the value of the following expression :```[pow(Ax, p) + pow(A(x + 1), p) + … + pow(Ay, p)]7```

Input

In the first line of the test case, there are two positive integers n(where 1<=n), which represents the length of the array.

Then, input operations sequentially, where each operation occupies one line, and the input will be 4 positive integers as in: type x y num, where type is either 1, 2, 3, or 4; these identifiers correspond to the corresponding operation as described above. The meaning of x and y corresponf to the description (where 1<=x<=y<=n). When type is not 4, num will be the positive integer given c(where 1<=c<=10000); when type is 4, num will be the given positive integer p(where 1<=p<=3)。

Output

For each test case, for every 4 operation for the array, output the value of the corresponding expression.

Example input

5
3 3 5 7
1 2 4 4
4 1 5 2
2 2 5 8
4 3 5 3

Example output

307
7489

Answer 2

Answer chain: decreasing character scores

Assign a non-negative integer value to each letter in the alphabet, and write a function or program which takes as input a character string and outputs the sum of of the values of the letters in the string. Characters outside of [a-z] and [A-Z] have value 0.

Now run your code, taking as input the code of each of the previous answers in the order they were posted (including your own). The resulting sequence of scores should be strictly decreasing.

For example, if you are 4th to answer and your code defines a function \$f\$, then the output should verify \$f(c_1)>f(c_2)>f(c_3)>f(c_4)\$ where \$c_1\$ is the code of the 1st answer, \$c_2\$ is the code of the 2nd answer, ..., \$c_4\$ is the code of your answer.

When there will have been one week with no new answer, the 2nd-to-last answer will be declared the winner.

Clarifications:

• The values you assign may be the same as or different from those used by previous answers.
• The value 0 is allowed.
• Different letters may be assigned the same value.
• Upper and lower case versions of the same letter may have different values.
• Letters with diacritics, such as é or Ä, have value 0.
• Your code need not handle letters which have not occurred in any of the previous answers (so if no answer so far has used the letter W, it's OK if your code fails on strings with a W).

Answer 3

Enable 2-char Jsfuck

Provide a shortest code that makes JavaScript able to do everything JavaScript is supposed to do, i.e. able to access(so no deleting [].prototype.toString unless you have a backup, even if you can simulate one [].prototype.toString) and exec anything, with only [ and ]. You can choose your environment(FF/node/etc). Answering in 6-char JsFuck or something similar is welcomed.

E.g. If you run

Array.prototype[''] = 'a';
Array.prototype['a'] = 'b';
Array.prototype['b'] = function() { console.log(this[0]); };

then [][[]] = [][''] = 'a', and [][[][[]]] = []['a'] = 'b', so [[][[]]][[][[][[]]]] = ['a']['b'] = function(){console.log('a')}.

Of course, this is an invalid answer, because it can't do prompt(web browser) or fs(node) or anything similar, or even calling the console.log.

Answer 4

Tips for golfing in H

As for H as described here, what general tips do you have for golfing in H? I'm looking for ideas which can be applied to code-golf problems. Tips have to be specific to H (e.g. "remove comments" is an answer).

Tips in Standard H are also on-topic, although its spec is in a bad condition. You can use the H description provided in the first link to solve anything you don't understand about.

Please post one tip per answer. Also, please specify which H implementation you are using if your code runs only under a specific H implementation, as different H implementations can have different behavior.

---

code-golftips

Answer 5

Find the closest hex colour shorthand

In CSS, colours can be specified by a "hex triplet" - a three byte (six digit) hexadecimal number where each byte represents the red, green, or blue components of the colour. For instance, #FF0000 is completely red, and is equivalent to rgb(255, 0, 0).

Colours can also be represented by the shorthand notation which uses three hexadecimal digits. The shorthand expands to the six digit form by duplicating each digit. For instance, #ABC becomes #AABBCC.

Since there are fewer digits in the hex shorthand, fewer colours can be represented.

The challenge

Write a program or function that takes a six digit hexadecimal color code and outputs the closest three-digit color code, where closeness is measured by adding together the difference between each component of the full color code and the corresponding component of the shorthand color code.

Here's an example:

• Input hex code: #28a086
• red component
  • 0x28 = 40 (decimal)
  • 0x22 = 30
  • 0x33 = 51
  • 0x22 is closer, so the first digit of the shortened color code is 2
• green component
  • 0xa0 = 160
  • 0x99 = 153
  • 0xaa = 170
  • 0x99 is closer, so the second digit is 9
• blue component
  • 0x86 = 134
  • 0x77 = 119
  • 0x88 = 136
  • 0x88 is closer, so the third digit is 8
• The shortened color code is #298

Your program or function must accept as input a six digit hexadecimal color code prepended with # and output a three digit color code prepended with #.

Examples

• #FF0000 → #F00
• #00FF00 → #0F0
• #D913C4 → #D1C
• #C0DD39 → #BD3
• #28A086 → #298
• #C0CF6F → #BC7

Answer 6

Golf an H quine [duplicate]

Your task is to write a quine program in H (described in my esolangs.org userpage). (It is unclear whether it is possible.) Referring to Computer Science stack exchange, which seems unappropriate.

---

code-golfcode-challengestringquine

Answer 7

Machine Learning Golf: Fashion MNIST

The first instance of Machine Learning Golf received a lot of intention but also revealed some problems (mostly caused by people in this community being too clever ;-)).

I intend to address those issues in this second installment:

Fashion MNIST is a dataset of 60,000 labelled 28x28 pixel grayscale images of fashion items (T-shirts/tops, Trousers, Pullovers, Dresses, Coats, Sandals, Shirts, Sneakers, Bags and Ankle boots).

Your task is to design and train a neural network that correctly identifies these images. Here are the rules:

Performance Goal

To qualify, your model must achieve at least 95% accuracy on the training set (i.e. you must identify at least 57,000 images correctly).

Rules

You may use any language and framework of your choice.

Your dataset must be taken as the current version of Fashion MNIST found here or in the references listed in that repo's README (for convenience).

You may reshape, permutate, rescale and offset entries in the dataset. However, modifications made to one entry must be performed on all entries.

You may transform the labels any way you like. (But you may, obviously, not change which labels correspond to which images.)

During training, you're allowed to use any dataset you want (in fact, you are allowed to come up with your weights however you like). Hence the above limitations are only relevant to assess whether your model meets the stated performance goal.

Your model

• must be a 'traditional' feed forward neural network, i.e.a node's value is calculated as a weighted linear combination of some of the nodes in previous layers (which may include a bias node with constant value 1) followed by an activation function. Note that this allows you to skip layers and use convolutional/residual layers,
• may only use the following standard activation functions:
  1. \$\mathrm{linear}(x) = x\$,
  2. \$\mathrm{softmax}(\vec{x})_i = \frac{e^{x_i}}{\sum_j e^{x_j}}\$,
  3. \$\mathrm{selu}_{\alpha, \beta}(x) = \begin{cases} \beta \cdot x & \text{, if } x > 0 \\ \alpha \cdot \beta (e^x -1 ) & \text{, otherwise} \end{cases}\$,
  4. \$\mathrm{softplus}(x) = \ln(e^x+1)\$,
  5. \$\mathrm{leaky-relu}_\alpha(x) = \begin{cases} x & \text{, if } x < 0 \\ \alpha \cdot x & \text{, otherwise} \end{cases}\$,
  6. \$\tanh(x)\$,
  7. \$\mathrm{sigmoid}(x) = \frac{e^x}{e^x+1}\$,
  8. \$\mathrm{hard-sigmoid}(x) = \begin{cases} 0 & \text{, if } x < -2.5 \\ 1 & \text{, if } x > 2.5 \\ 0.2 \cdot x + 0.5 & \text{, otherwise} \end{cases}\$,
  9. \$e^x\$
• must take a single entry of the (preprocessed) training set as its only input and
• return the predicted label, in the format you've specified, as its only output,
• if a given weight occurs multiple times in your model, you may reuse it to lower your overall score,

Your answer must include (or link to) all code necessary to check your results -- including the trained weights of your model. In particular, you must include all preprocessing steps of your dataset.

Scoring

The neural network with the smallest number of weights (including bias weights) wins.

Parameters used to preprocess your data don't count as weights.

Enjoy!

Baseline

There is a tutorial for the Fashion MNIST dataset available on Tensorflow which serves as an excellent starting point if you decide to use TF as your framework.

---

This challenge had already been posted on the main site and got closed there. The purpose of this post is threefold:

1. Is the community interested in this particular (and this kind of) challenge (in general)?
2. How can the user experience for the target audience be improved? Specifically:
   • What are likely causes of confusion?
   • Can we streamline the structure?
   • Are some of the rules too restrictive or not restrictive enough?
   • Are there any loopholes I've overlooked? (For instance, preprocessing the training data opens up the possibility of encoding labels into the feature set. Some of the rules are already designed to prohibit this but it's entirely possible that they don't suffice.)
3. Any other constructive feedback?

Answer 8

Calculate a constant from its characteristic function

You are given in some language-dependent way (e.g. a lambda parameter) a characteristic function which is basically another way of saying a decision-problem function. This function will take an integer input and return true or false, or 1 or 0, or any other two 1-byte values of your choice. You can decide whether you need the function to be 0-indexed or 1-indexed.

Your job is then to take this function and calculate the floating-point value obtained by interpreting the values of this function as a binary fraction. You must use as many significant digits as possible. I will assume IEEE double precision by default but you many use single precision if your language specifically supports it.

For example, if a function returns the sequence 0, 1, 1, 0, 1, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0 (this is OEIS A010051), then your program or function will output 0.41468250985111166 as any further terms will be less than the precision of a double-precision value.

You can decide whether you want to round the 54th significant bit up or not.

This is code-golf, so the shortest program or function that breaks no standard loopholes wins!

Answer 9

answer-chaining

Make a bigger number

Each answer on this question must be a complete program (not a function) that outputs a positive integer in decimal (trailing newlines are permitted). Output should be either passed to STDOUT or displayed on the screen. The output number must also be larger than all the numbers output by all the valid answers at the time of posting. One person may not post two consecutive answers.

Scoring

Your answer will be scored with the following formula

\$\dfrac{B'+1}{B+1}\$

Where \$B\$ is the number of bytes in your answer and \$B'\$ is the number of bytes in the longest answer before your answer posted by someone other than yourself. Lower scores will be better.

Answer 10

Output Ordinal Numbers up to n

Moved to Output Ordinal Numbers up to n.

Answer 11

Write an X-SAMPA Interpreter

Tags: code-golfunicodestringinterpreter

Write an X-SAMPA interpreter that, when given an X-SAMPA string, outputs an IPA string.

Some Background

SAMPA is a system for encoding sounds from various languages into a computer-readable ASCII format. X-SAMPA is a descendant that encodes the International Phonetic Alphabet (IPA) instead. The IPA is a character set that represents (almost) all sounds that a human can make. A large majority of IPA is based on the usual Latin character set (a-z), along with some supplementary characters (θ ʌ ŋ χ, etc.).

The Challenge

• Input is a string of X-SAMPA.
• Translate the X-SAMPA string into IPA.
• Output is a string of IPA.
• Input and output can be given using any convenient method.
• Standard loopholes are forbidden.
• X-SAMPA charts can be found here.
• Characters not defined in X-SAMPA should be ignored.
• You must implement the entirety of X-SAMPA.
• This is code-golf so lowest in bytes wins.

Samples

this is a test input --> this is a test input
THIS IS A TEST INPUT --> θɥɪʃ ɪʃ ɑ θɛʃθ ɪŋʋʊθ
H\El\L\0 W@R1d --> ʜɛɺʟ0 ʍəʁɨd
123456789 --> ɨøɜɾɫɐɤɵœ
d_"i_+a_-c_/r_/i_0t_hi_=c_>s_?\ --> d̈i̟a̠čři̥tʰi̩cʼsˤ
Code GO\lf & CodI\ng Challen\ges\ --> çode ɣʘlf ɶ çodᵻnɡ çhallenɡeɕ
clicks O\|\ǃ\=\|\|\ --> clicks ʘǀǃǂǁ
mixed~!@#$%^&*(){}[]<>,.?/:;"' --> mixed#$ˌ^ɶ*(͡æʉ[]<>,.ʔ
impl ejec b_<p_> --> impl ejec ɓpʼ

Answer 12

Brute-force the switchboard

Posted here!

Answer 13

The Acrobat Competition

Anyone may post this to main once this question is done. I only care about people enjoying solving problems. (I do not want the reputation for this question.)

After someone cloned so many Jimmy's to disrupt the world, Jimmy started to be stressed about the existence of his dwarf forms; his circus leader started to ignore him, focus on the dwarves, and gradually gave him less salary.

He has to win an acrobat competition to gain attention from his leader again. (He does care about his salary.)

Input/Output

The first line of input will contain the acrobatic power of Jimmy; it is represented as Jimmy's (/o\) separated with spaces; invalid Jimmy's should be ignored.

After this line, there are two lines of dwarf Jimmy's also represented by their shapes: (o); invalid dwarf Jimmy's should be ignored.

The combined power between two dwarf (x as the top line of dwarf Jimmys and y as the bottom line of dwarf Jimmys) is √x²+y² (the exact floating-point number).

If Jimmy's acrobatic power is larger than the two dwarf Jimmy's, output a truthy value. Otherwise, output a falsy value.

Example input/outputs

This outputs a falsy value:

/o\ // o /o\ o o\ //o\\ /o\ /o\ /o\
o o o o
/o\ l o j oe o lo . o aso o feo o

This outputs a truthy value:

/o\/o\ /o\ /o\ /o\ /o\ /o\ /o\
o	o o 	 o
o	o o o	o o oo o o o o

Answer 14

Insert an exclamation mark between everything

This challenge is highly "distilled" from this question. Special thanks to Akababa!

In this task, you should insert an exclamation mark at the start of the string and after every character.

Rules

• There will always be a non-empty-string input. The input will not contain tabs either. You can assume that the input only contain non-extended ASCII printable characters and newlines.
• This is a code-golf contest; the shortest answer should win.

Examples

• 4 newlines result in 5 newline-delimited exclamation marks. It is very hard to put this as a Markdown text, so this is stated instead.

1 2 3 4 5 6
129591 129012 129127 129582

0

Outputs

!1! !2! !3! !4! !5! !6!
!1!2!9!5!9!1! !1!2!9!0!1!2! !1!2!9!1!2!7! !1!2!9!5!8!2!
!
!0!

asd afjoK ak:e
kPrLd
    fOJOE;
    KFO
KFkepjgop sgpaoj   faj

Outputs

!a!s!d! !a!f!j!o!K! !a!k!:!e!
!k!P!r!L!d!
! ! ! ! !f!O!J!O!E!;!
! ! ! ! !K!F!O!
!K!F!k!e!p!j!g!o!p! !s!g!p!a!o!j! ! ! !f!a!j!

A base test case with only one character:

a

Outputs

!a!

(Auto-completion! Just kidding, there is no such thing.) Contains exclamation marks:

!!
!!
!!
!!
!!

Outputs:

!!!!!
!!!!!
!!!!!
!!!!!
!!!!!

---

code-golfstring

Answer 15

Give me the jitters! / Add noise to data

When graphing data, it can often be helpful to display points as a scatterplot, but when duplicate data exist, you'll have multiple points graphed on top of one another. For fairness, we break ties at random with R's jitter function.

Inputs

• x, a numeric (floating point) array. There will be at least 3 distinct values in the array.
• factor, a numeric value
• amount, a numeric value or some sort of non-numeric value (your choice). You may select your desired non-numeric sentinel value for amount.

Output

• A single array y where:
  • y[i] = x[i] + a uniformly random number from -a to a

a is defined as follows:

• Let z = max(x) - min(x)
• If amount==0, a = factor * z/50
• If amount is NULL or the , a = factor * d/5 where d = min(diff(sort(unique(x)))), i.e., the smallest difference between adjacent unique values.
• Otherwise, a = amount.

---

Add test cases

code-golf random

Does this add anything beyond already existing challenges?

Answer 16

Output your place

code-golf internet

---

Your challenge is simple. Output your program's place as an integer at the time of execution. The shortest program is first place, and the earlier submission wins a tie.

If your solution is tied with another in age as well as length, you may output either

All answers must begin with # [Language Name], [N] bytes alone on the first line.

You may access this page (URL). No URL shorteners are allowed. Standard IO and loophole rules hold.

As you may have noticed, this is code-golf, so the shortest answer (in bytes) wins. Happy golfing!

Answer 17

Buffer Evaluation

Given a printable ASCII string, but with leading spaces(0x20) and backspaces(0x08), return it "buffer-evaluated".

Input

For the inputted line, if you encounter a space, enter a space; otherwise, remove the rightmost character.

If you encounter a backspace when the buffer is empty, simply do nothing.

Output

After the inputted program, if the cursor is 0, output an optional trailing newline. If the cursor is not 0, output the string in the buffer and an optional trailing newline.

Example(s) and expected output

Rules

This is code-golf; the shortest answer wins.

---

code-golf string

Answer 18

Do X without Y

code-golfgraphical-output The goal is drawing an X on an empty 3x3 raster "canvas". You have to do so by drawing pixel by pixel, showing each intermediate step. But there should never be an Y visible along the way.

Details

• You should start by outputting a 3x3 image of one background color. In each step one of the pixels must be changed to the foreground color.
• You can use any two colors.
• Instead of using pixels in an image, you can also use a string- (leading/trailing zeros/newlines are ok) or 2d-array/matrix representation.
• An X is represented as follows:

o.o  (o = foreground, . = background)
.o.
o.o

while an y can be any of the following

o.o  o.o  ..o  o..  
.o.  .o.  .o.  .o.
o..  ..o  o.o  o.o

(title reference)

Answer 19

Crossing Sequences

Posted.

Answer 20

A triangle is worth a thousand lines

Vulkan is a relatively new cross-platform graphics API which is very powerful yet extremely verbose and detailed.

Arguably one of the most infamous saying on Vulkan, especially among beginners is, "The 1000 Lines journey". That is, getting a simple triangle to render on the screen takes a ton of code (~1k lines of C/C++).

It's time to break, nay, golf the stigma!

Challenge

Your challenge is writing a valid Vulkan-API based program which outputs a triangle to the screen. The windowing system is up to your choice as well as the colors/size of the triangle/screen itself.

The final script/compiled program should be able to be executed (preferably on a platform which does not require extra tools/hardware) and the output made visible in order to count as a valid solution.

Input

None. (Any if you require it, but it will also account into the score)

Output

A visible triangle on the screen. The following rules apply:

1. The color of the triangle and the color of the background should be different.
2. The size of the triangle should be noticeable. That is, any person with healthy eyesight should immediately be able to notice it.

Note: The final output triangle must be an actual call to drawing a 3 vertexed mesh and not simply points which render to some 4 pixels on screen.

Hardware constrains

Since the setup code differs greatly from GPU to GPU, you can assume that all the extensions are supported and that the GPU/driver is capable of executing a valid API call. Namely, input validations aren't mandatory, swapchain is present, queues are optimal, etc...

Scoring

Standard 1 (source code) byte = 1 point scoring, less is better. (The shaders source file sizes also counts towards the final score)

Note There are currently but a few available bindings for Vulkan which means that the language choice isn't as wide as other challenges. However, there is plenty to choose from with different paradigms, thus it shouldn't harm the creativity of the solutions :)

Helpful resources

• Language bindings
• Specification
• OpenGL (Vulkan's predecessor) and a tutorial for it (mainly because it explains some of the aspects in much less code)
• GLSL specifications, the language which defines the source code of the shaders used.

Answer 21

Get the number of upvotes of your own answer

Write a piece of code which makes a request to codegolf.stackexchange.com and prints the, up to date, number of upvotes to the specific answer in which you've posted that piece of code.

As a test case I'll post a (poor!) answer below (obviously only in the real question).

This is just a random idea I had when reading some other code golfing challenges, and I thought I'll post it here to see if it will fly.

Answer 22

Approaching the Graham's number cops-and-robbers

Write a program that could theoretically output an integer with the minimum absolute difference to the Graham's number. Your code is cracked if a robber writes a program to output the Graham's number exactly, in the same language, with the edit distance to your code under a specific limit.

Builtins for the Graham's number is disallowed.

Details to be added, if I think this idea actually works.

---

Problems:

How to set the limit?

1. Fixed number of bytes.
2. Fixed % of the code. Does the boilerplate count?
3. Set by the cop. But how to fix the winning criterion?

Do the cops need to know a crack to make the submission valid?

Answer 23

"Condense" String of Text

You will be given a string. You will be "condensing" it by combining the bits of characters into one.

Rules

• The condensation works as follows:
  1. You are given a string with 8-bit characters, such as Hèl¹ò Wôrld, hex 48 e8 6c b9 f2 20 57 f4 72 6c 64
  2. Combines bits into 16-bit groups, from right to left. Above becomes hex 48 e86c b9f2 2057 f472 6c64, or H槲⁗汤.
• You may assume that all characters in string range from 0x00 to 0xff.
• Your resulting string would be encoded in UTF-16.
  • You may also assume that the resulting string won't contain characters from 0xd800 to 0xdfff, or the input containing any of ØÙÚÛÜÝÞß at even index in 0-index, or odd index in 1-index.
• Standard loopholes apply.
• This is code-golf so shortest code wins.

Examples

Input raw: abacaba
Input hex: 61 62 61 63 61 62 61
Outpt raw: a扡捡扡
Outpt hex: 61 6261 6361 6261

Input raw: Example.
Input hex: 45 78 61 6d 70 6c 65 2e
Outpt raw: 䕸慭灬攮
Outpt hex: 4578 616d 706c 652e

Input raw: ÿ!0ÿMÿEÿSÿSÿAÿGÿE0ÿCÿAÿN0ÿAÿPÿPÿEÿAÿR0ÿTÿOÿOÿ
Input hex: ff 21 30 00 ff 4d ff 45 ff 53 ff 53 ff 41 ff 47 ff 45 30 00 ff 43 ff 41 ff 4e 30 00 ff 41 ff 50 ff 50 ff 45 ff 41 ff 52 30 00 ff 54 ff 4f ff 4f ff 0e
Outpt raw: Ａ　ｍｅｓｓａｇｅ　ｃａｎ　ａｐｐｅａｒ　ｔｏｏ．
Outpt hex: ff21 3000 ff4d ff45 ff53 ff53 ff41 ff47 ff45 3000 ff43 ff41 ff4e 3000 ff41 ff50 ff50 ff45 ff41 ff52 3000 ff54 ff4f ff4f ff0e
Note that there are NULs in the input.

Answer 24

Break it up and put it back together again

code-golf restricted-source

Note: This is restricted-source, so read carefully and make sure your answer is valid before posting.

Write a program/function that takes a list of integers greater than 1 and returns a list of positive integers where each number from the original list has been split in two. For example:

[10,11,12] -> [5,5,4,7,6,6]

Each pair of numbers in the output add up to the corresponding number in the input. The algorithm used to split it up doesn't matter (for example a valid output could be [1,9,1,10,1,11]), as long as it is deterministic.

However, when fed its own byte values and the output is turned back into bytes, the resulting program should do the opposite, taking a list of integers and summing each pair. For example, if the program abcde splits each number into halves, with the leftover going to the second number:

"abcde" -> [97, 98, 99, 100, 101]
-> [48, 49, 49, 49, 49, 50, 50, 50, 50, 51] -> "0111122223"

The program 0111122223 should then be able to take the list [48, 49, 49, 49, 49, 50, 50, 50, 50, 51] and return the original [97, 98, 99, 100, 101]

Notes/Rules

• Output must be deterministic
• Output can't be a list of lists (no list of pairs)
• The second program may assume that the length of the input is even (so you don't need to account for a leftover element)
• Submissions can be functions, programs or different for either part
• Remember, output must be a list of positive integers.
  • You won't get 1 in the input of the first program
• The programs have to be in the same language
• Input can be a string or list of characters instead

Answer 25

Golfed User-Pinging

In this task, given a user's display name(e.g. Display Name) from which the first space has been removed, use the API to find a user it could be and output their display name up to the first space. Both input and output must have an @ prefixed to them.

The input will not contain spaces in it, so you have to search for the user before doing this.

If the user does not exist, do anything else other than outputting the golfed user ping. (That includes outputting to stderr.)

Rules

• This is a code-golf contest; the shortest answer wins.
• No standard loopholes allowed. (In fact, hard-coding the answers will annoy other users, as you pinged all of them.)
• The space (U+0020) is the word separator.
• Input will not contain display names containing 2 or more spaces.
• In addition to golfing the code, the answers also have to use as few calls as possible. (Due to the rate limiting of the API)
• The input will always be case-insensitive and are restricted to printable ASCII.

  Examples

@Dennis -> @Dennis
@MartinEnder -> @Martin
@Cowsquack -> @Cows
@JB -> @J
@tsh -> @tsh
@cairdcoinheringaahing -> @caird

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Sandbox

• Is it a duplicate?
• Do you understand everything here?
• Any suggestions for test cases?
• Most importantly, can you cheat over this challenge by using an algorithm not requiring network access?

code-golfstringinternetstack-exchange-api

Answer 26

Self-fibonaciing prophecy

Where L is the length in bytes of your source code
and n=(L+2)^2

Your program or function should output Fib(n)

Your program or function should take no input, and output according to the usual code golf rules

This seems like a very simple task, but the (L+2)^2 part is designed to prevent single digit outputs which could be hard coded in many languages, and ensure the required output will usually be longer than the source code, so it should produce some interesting mathematical answers

Question for meta - Is (L+2)^2 suitable for this?
Another possibility I have considered is (L^2)+8 which would grow a bit slower but still achieve the goal of preventing trivial solutions
Having a look at this again, I think the sequence still grows too quickly. Maybe n=ceil(L^1.5)+18 would be more reasonable

Another question for meta - Should I include a link to a source of Fibonaci numbers, or is it safe to assume readers know what this is and can find it for themselves?

Answer 27

Compare Multiratios

EDIT: No doesn't make any sense, I need to think about it again.

Answer 28

Smallest self-hosting golfing language code-golf

Implement a golfing language that is implemented in itself. Formally speaking: The original compiler O (an executable file assumed to be implemented in other language X), when given its own source code S (in golfing language G), must produce the identical executable file O. Your task is to create G by implementing O.

Language X might be an ELF binary, x86 assembly, Python, LLVM IR, etc.

Neither your language implementation S or executable file O may use functions that have the same functionality as exec or eval. That is, you may not use any built-in code evaluation of your compiler O. Standard Quine loopholes, such as reading your own file, downloading your file from the internet, and holding the program data in the filename, are not allowed.

The executable file O of the compiler must not be embedded in any shape or form in the source code S of the compiler. Additionally, the source code S of the compiler must be strictly shorter than the executable file O.

Your code must not be dependent on any external program or internet resource other than language X: if your language is dependent, include the size of the external dependencies in your submissions. Your program gets a standard POSIX system base for free, plus GCC 8 and LLVM 10: you do not have to include the size of this in your submission. For example, if you submitted a Bash Quine that just invoked the 05AB1E interpreter via the command line, you would have to include both the size of the the 05AB1E implementation, as well as the size of the Elixir implementation (since 05AB1E is implemented in Elixir and your base language X isn’t Elixir) in your bytecount.

In addition, standard golfing loopholes apply.

Requirements

Answer at least 10 other code-golf challenges on this website, beating at least 50% of the existing answers in byte size.

• Only challenges that already have 4 answers are allowed
• Your own other answers to the challenges do not count
• Challenges newer than this post are allowed, as well as answering your own challenges; provided they already have 4 answers from other answerers
• Link to your challenge answers for verification

Base language X restrictions

Language X must have an implementation, in other words we must be able to actually run your compiler O with source code S and get compiler O as output.

Language X must have already existed before this post was created.

You are encouraged to share the techniques of how you created your compiler and how you came up with your golfing language.

Scoring

$$S*0.98^{(n-10)}$$ where n is the number of challenges where you beat at least 50% of the other answers, not including your own.

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Feedback

How can you prevent someone submit a zero bytes answer and claim: if source is empty, it output the interpreter, otherwise output compiled python code. – tsh Aug 24 at 4:42

Answer 29

DRAFT: Remove vertical comments code-golf

Vertical commnets...

        /> push back with    result.cows_used.push_back(possiblecow);
        the new cow added </ cows_used.push_back(result.cows_used);

Traditional comments...

        /* push back with */ result.cows_used.push_back(possiblecow);
     /* the new cow added */ cows_used.push_back(result.cows_used);


        result.cows_used.push_back(possiblecow);
        cows_used.push_back(result.cows_used);

Annotated, everything with . is considered a comment:

        />.................. result.cows_used.push_back(possiblecow);
        ..................</ cows_used.push_back(result.cows_used);

What is both between the start row of /= and the end row of =/ and between the start column of /= and the end column of =/ is considered a comment.

        /> push back with       result.cows_used.push_back(possiblecow);
           the new cow added </ cows_used.push_back(result.cows_used);

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Todo

• Add testcases

Answer 30

Breaking the Wordbuilder (canned)

Dupe of Let's Play Countdown! ... oh well. Thanks for the feedback everyone.