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.

Sandbox FAQ

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Answer 1

Output Ordinal Numbers up to n

Moved to Output Ordinal Numbers up to n.

Answer 2

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 3

Brute-force the switchboard

Posted here!

Answer 4

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 5

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 6

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 7

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 8

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 9

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 10

Crossing Sequences

Posted.

Answer 11

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 12

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 13

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 14

"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 15

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 16

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

---

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 17

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 18

Compare Multiratios

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

Answer 19

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.

---

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 20

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);

---

Todo

• Add testcases

Answer 21

Breaking the Wordbuilder (canned)

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

Answer 22

I see your BIDMAS and raise you a BADMIS

Challenge

Given a set of numbers with operators between them: "5 + 4 * 9 / 3 - 8", return all the possible results of the expression for every permutation of the order of basic operations: [/, *, +, -].

Rules

• Standard loopholes forbidden
• I/O
  • Input must be ordered with infix operations, but however that is easiest (string or array)
  • Output must be all of the possible results of the expression, no specified format or order, no repeats
• All of the inputs are valid (e.g. do not need to deal with "7 / 3 + *"
• Operators are all left-associative so "20 / 4 / 2" = "(20 / 4) / 2"
• This is Code Golf so fewest number of bytes wins

Test Cases (With explanation)

• "2 + 3 * 4" = [14, 20]
  • 2 + (3 * 4) ⟶ 2 + (12) ⟶ 14
  • (2 + 3) * 4 ⟶ (5) * 4 ⟶ 20
• "18 / 3 * 2 - 1" = [11, 6, 2, 6]
  • ((18 / 3) * 2) - 1 ⟶ ((6) * 2) - 1 ⟶ (12) - 1 ⟶ 11
  • ((18 / 3) * (2 - 1) ⟶ (6) * (1) ⟶ 6
  • (18 / (3 * 2)) - 1 ⟶ (18 / (6)) - 1 ⟶ (3) - 1 ⟶ 2
  • 18 / (3 * (2 - 1)) ⟶ 18 / (3 * (1)) ⟶ 6

Test Cases (Without explanation)

• "45 / 8 + 19 / 45 * 3" = [5.765740740740741, 0.01234567901234568, 0.11111111111111113]
• "2 + 6 * 7 * 2 + 6 / 4" = [154,113.5,88]

Answer 23

The Rattlin' Bog

There's a relatively famous Irish Folk song called The Rattlin' Bog, a type of cumulative song.

Basically, this is a song that alternates between a chorus and an ever-expanding verse

The chorus is as follows:

Ho, ro, the rattlin' bog
The bog down in the valley-o
Ho, ro, the rattlin' bog
The bog down in the valley-o

Each verse starts with
And on that [x] there was a [y]
A rare [y], a rattlin' [y]

and ends with
In the bog down in the valley-o

Where x is the word from the previous round, and y is the word for the current round. In between these two is the cumulative part. It starts with:
The [z] in the bog

Each new round adds
The [y] in the [x] and
To its predecessor.

Challenge

Given a list of strings, character arrays, or whatever reasonable equivalent collection of string or your language equivalent thereof, Your job is to print the lyrics to the song, alternating between the chorus and each verse, starting and ending with the chorus. The chorus and verse must be separated by a pair of newlines.

For the sake of brevity, you may write the chorus once, preceded by "[Chorus]" then write "[Chorus]" in place. I'm also omitting any sort of final verse with unique text.

Example:

Input: [House, Roof, Nest] 
Output:
[Chorus] 
Ho, ro, the rattlin' bog 
The bog down in the valley-o 
Ho, ro, the rattlin' bog 
The bog down in the valley-o  

And on that bog there was a House
A rare House, a rattlin' House
The House in the bog
In the bog down in the valley-o

[Chorus]

And on that House there was a Roof
A rare Roof, a rattlin' Roof
The Roof in the House and the House in the bog
In the bog down in the valley-o

[Chorus]

And on that Roof there was a Nest
A rare Nest, a rattlin' Nest
The Nest in the Roof and the Roof in the House and the House in the bog
In the bog down in the valley-o

[Chorus]

Answer 24

Sliding window minimum code-golf restricted-complexity

The task is, given a number array of length n and a positive integer k, to compute the smallest values in all its overlapping consecutive subarrays of length k in the order they occur.

The complexity of your program should be no more than linear with respect to n with a constant added.

Input

A positive integer array of length n and a positive integer k (k <= n)

Output

A positive integer array with n - k + 1 elements, where the element at position i equals the least number in the subarray starting at i and ending at i + k - 1 inclusive.

Examples

[1, 3, 5, 7], 2 -> [1, 3, 5]
[1, 3, 5, 3, 5, 1], 3 -> [1, 3, 3, 1] 

TODO

Sandbox stuff

• Is it acceptable to combine code-golf with restricted-complexity?
• Is the complexity restriction clear enough?
• Is it a good idea to allow calculating the maximum instead of the mininum?
• Is the grammar correct enough?
• Has this been posted before?
• Do any languages have built-ins for this?

Answer 25

Random point on a sphere

Posted here

Answer 26

Consequence Golf

code-golfgolf

As specified by this xkcd, Consequence Golf is a game involving golfing and bombs. The most obvious consequence of bombs: damage to the course.

A Consequence Golf course consists of the union of several circular regions. The tee is located at (0, 0). On each turn, you hit the ball bomb in a direction at some power. The bomb will travel in that direction for a distance equal to the power of the shot, unless it hits the edge of the course, in which case it will explode immediately. When a bomb explodes, it adds to the course a new circle centered on the point of contact with a radius equal to the remaining power. The next shot starts at the last location of the bomb.

Input

• A list of circles, consisting of x/y coordinates and a radius for each circle, taken in any convenient format. If you must define a custom data type to store this information (e.g. struct c{float x,y,r};), you do not need to count that added boilerplate, nonproductive storage code in your byte count. Any code that does something besides specify storage must be counted.
• A list of strokes, consisting of an angle in radians or degrees, and a power, again in any convenient format.

Output

• The location of the bomb after the final stroke.

Additional Rules

• The course will always contain at least one circle
• The course will always contain the tee at (0, 0)
• If there are zero strokes, you must return (0, 0)
• The power of a stroke will never be zero
• "Any convenient format" means a list of lists, list of C structs, a list for each input (x, y, radius, power, angle), or similar. You may not take information that is not as it is specified. For example, you may not take the circles as a series of equations.
• This is consequence code golf, so shortest code in bytes wins.

Test cases

TBD...

Questions for META:

• Is the description of how to play Consequence Golf clear enough?
• Is the description of the input clear enough? This is my main concern.
• Is allowing boilerplate storage code outside of the byte count an issue?
• I am considering allowing fixed point approximations with at least 4 bits of precision for languages without floating point (and languages with, if it somehow makes things shorter). Would this cause any unintended issues?

Answer 27

Posted to PPCG

Answer 28

Encode MC6000 instructions

In MC6000, these are registers list:

acc  general
dat  general
p0   simple pin
p1   simple pin
x0   XBus pin
x1   XBus pin
x2   XBus pin
x3   XBus pin
null pseudo

where general means reading from it returns the last value written to it, XBus pin means reading from or writing to it have side effect(so teq x0 x1 doesn't equal to teq x1 x0) that nothing else can take its place, simple pin means reading from it also writes zero to it(so mov 0 p0 equals to mov p0 null), writing anything to it(including the writing while reading) have side effect, and writing anything larger than 100 behaves same as writing 100, as well as writing anything smaller than 0 same as writing 0(so mov -4 p0 equals to mov 0 p0). Writing anything into null has no effect and reading from null returns 0(so mov 9 null equals to nop).

The instruction set is:

nop            Do nothing
mov R/I R      operand2:=operand1
jmp L          Jump to the specified line(can't be replaced)
slp R/I        Sleep for the number of time units specified by the operand.
slx XP         Sleep until XP avaliable(can't be replaced)
add R/I        acc:=f(acc+operand)
sub R/I        acc:=f(acc-operand)
mul R/I        acc:=f(acc*operand)
not            acc:=100(if acc was 0) or 0(otherwise)
dgt R/I        acc:=(acc/10^operand)mod 10(if operand in 0,1,2) or 0(otherwise)
dst R/I R/I    acc:=[abs(acc-[(acc/10^operand1)mod 10]*10^operand1)+abs(operand2 mod 10)*10^operand1]
               *sgn(operand2*2+1) (if operand1 in 0,1,2) or acc(otherwise)
teq R/I R/I    sym:='+'(if operand1 equals to operand2) or '-'(otherwise)
tgt R/I R/I    sym:='+'(if operand1 is larger than operand2) or '-'(otherwise)
tlt R/I R/I    sym:='+'(if operand1 is smaller than operand2) or '-'(otherwise)
tcp R/I R/I    sym:='+'(if operand1 is larger than operand2),
               '-'(if operand1 is smaller than operand2) or '*'(otherwise)
gen SP R/I R/I Output 100 and 0 to the simple pin for the latter two operands, inclusive

Here R/I means a register or an integer between -999 and 999, inclusive; R means a register, L means an integer between 0 and 13, XP means an XBus pin, and SP means a simple pin. f(x) is defined as min(999,max(-999,x)). Sleeping for zero or negative time units sleep for time as long as a nop(so nop=slp 0=slp -3).

Before an instruction, symbol +, - and @ can exist, meaning that the instruction is executed only if sym is +, - and @, inclusive. (@ doesn't work like this in fact but that doesn't affect this problem) Whether the instruction is executed matters even if it's a no operand(so + nop doesn't equal to - nop, but + nop equals to + tgt 1 0).After an instruction, comment start with # can exist, which can be ignored. Spaces work as separator, and can be added or removed as long as words are separated in the same way(continious spaces, spaces at both side).

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Now, write a program A that, reads an instruction and output an integer; and write a program B that reads the output of program A and output an equal or same instruction fed into program A.

Your score will be the sum of length of program A, length of program B, and difference between the maximum and minimum of output of A. Lowest score in every language win.

Using MetaGolfScript is allowed. Only write MetaGolfScript in language area and show the exact version you use in code area to make it leaderboard friendly.

Answer 29

Tiling string

(inspired by the tiling pattern effect tipic of the texturing of landscapes. This question I would like to ask is not exactly the same thing but close to it, or at least it was the idea)

Given a string S check if it has some repeating tile pattern and prove it providing at least one repeating pattern.

A substring tile pattern is a pattern of any form which repeats inside the string where one or more(alpha case insensitive) chars forms a fixed structure that can contain also others generic chars(all printable ascii table set)

the output will be false,0,f or any meaningful negative expression if no tiling occours. true,1,... plus at least one repeating tile pattern instead.

for example :

 they were obsessed by the sessions
             s#ss          s#ss
 outputs : true s#ss



look at that truck
      t$t  t$t
outputs: 1,t$t


- case insensitive. 
- only letters matters as tile pattern.   
- if two letters are separated by space or every non letter char they still form a pattern.  
- overlaps doesnt make tiling effect.
- a pattern must contain half or more structure chars and must be len>1 to be considered, and must be repeated at least two times.

example

"Hello world!"=> false or 0 or f or no

"aa"=>false.
aaa=>false. "aaaa"=> true(aa)
"aabbabab"=>true:ab,ba or 1 ab ba. or yes[ba,ab] or...any reasonable format

This is code-golf so shortest answer wins

Answer 30

Observability and controllability

code-golf linear-algebra decision-problem

Background

Note: if you like, you can skip this part, and simply implement the suggested algorithm.

When looking at dynamic systems, there exist the notions of observability and controllability. They are the answers to the questions

• Observability: can we know all the internal states of a system by looking only at the given outputs?
• Controllability: can we influence all the internal states of a system by changing only the inputs?

For the sake of this question, we will only look at LTI (linear time-invariant) systems, either in continuous or discrete time. During the rest of the question, I will only present the case of a state-space representation of the system and suggest using the observability- or controllability Gramian, but you may use any other algorithm to decide the controllability and observability of the given LTI system.

Input

You are given an LTI system, $$ \mathbf{\dot{x}}(t) = A\mathbf{x}(t) + B\mathbf{u}(t)\\\mathbf{y}(t)=C\mathbf{x}(t)$$ where \$A\$, \$B\$ and \$C\$ are matrices containing only integers. The dimensions of these matrices are \$\dim{A}=n \times n\$, \$\dim{B} = n \times p \$ and \$\dim{C} = q \times n\$ with \$n\$, \$p\$ and \$q\$ positive integers.

A suggested input method would be to simply input these matrices, but you may also take input as function objects, string representations of differential equations, or transfer functions.

Output

You must output two thruthy/falsy values, one indicating whether the system is controllable, and one indicating whether the system is observable. Order does not matter but must always be the same. Alternatively, you may have four distinct outputs (e.g., the integers 0, 1, 2, 3) each corresponding to a possible combination of controllability/observability.

Suggested algorithm

To decide on observability and controllability, you can calculate the so-called observability Gramian (a square matrix), $$\begin{bmatrix}C & CA & CA^2 & ... & CA^{(n-1)}\end{bmatrix}^T$$ and controllability Gramian $$\begin{bmatrix}B & AB & A^2B & ... & A^{(n-1)}B\end{bmatrix}$$ The system is observable iff the observability Gramian is invertible. The system is controllable iff the controllability Gramian is invertible. There are many ways to check if a matrix is invertible; an obvious way would be to check if the determinant equals zero.

Testcases

Coming soon, because I want to include worked examples.