19
2
Write a program/method that:
This is code-golf, so shortest solution wins. Avoid any standard loopholes.
Dannyu NDos
Posted 2020-01-26T04:34:22.757
Reputation: 2 087
5
“Ṿ;⁾v`¹⁻³$¿”v`
A program taking a single string argument and either printing its source if the string matches its source, or looping indefinitely if not.
“ ”v` | Evaluate the following string as Jelly code, using the string itself as argument:
Ṿ | - Uneval (effectively wrap the string in “”
;⁾v` | - Append v`
⁻³$¿ | - While not equal to the original program argument:
¹ | - Call the identity function
Nick Kennedy
Posted 2020-01-26T04:34:22.757
Reputation: 11 829
13
exec(a:='print(s:=input())\nwhile s!="exec(a:=%r)"%a:1')
a='s=input();print s\nwhile s!="a=%r;exec a"%a:1';exec a
Mukundan
Posted 2020-01-26T04:34:22.757
Reputation: 1 188
2Is there anything in 3.8 that this answer relies on? – Cruncher – 2020-01-27T21:24:36.227
3
@Cruncher https://docs.python.org/3/whatsnew/3.8.html#assignment-expressions
– Aaron – 2020-01-27T22:07:01.1138
{`".~"+{.2$=}do\;}.~
{ }.~ # Evaluate the following string as GolfScript code, using the string itself as argument:
` # - Uneval (effectively wrap the string in ""
".~"+ # - Append .~
{.2$=}do # - Do While not equal to the original program argument:
# - (Basically do nothing)
\; # - If this loop ends, discard the extra copy of the input
3What is the relationship between Jelly and GS? – RGS – 2020-01-26T15:20:20.533
1@RGS It's simply because Jelly is (indirectly) based on GS. – None – 2020-01-26T22:52:56.940
1why did the GS port of a jelly answer get more votes than the answer it was porting? – Cruncher – 2020-01-27T21:25:35.250
5
"34çìD«Êi["34çìD«Êi[
"34çìD«Êi[" - string literal
34ç - push the character "
ì - prepend to the string literal
D« - duplicate the string (producing the code)
Êi[ - loop if it's not the same as the input
- else implicitly output
Expired Data
Posted 2020-01-26T04:34:22.757
Reputation: 3 129
2
eval($s='$a=chr(39);$b="eval(\$s=$a";$c="$a);";$b.$s.$c!=$argn?:die($b.$s.$c);for(;;);');
This is the best I have found so far, at the beginning it wasn't a port of @Mukundan's answer, but it pretty much ends like it. I will try to improve it later..
EDIT: saved a byte with != instead of == so I can remove the 1
EDIT2: saved 16 bytes using vars for repeated strings
Kaddath
Posted 2020-01-26T04:34:22.757
Reputation: 449
2
«•.x=xe²xw³1#1:?
«•.x=xe²xw³1#1:?<SPACE> #
« # Push the following function to the stack and execute
•. # Append a space (A non-function character) and stringify
x= # Assign the stringified function to x
xe # Is x equal to the top of the stack?
² # "Double Function" to execute if true
x # Push x to the stack
w # Output
³ # "Tripple Function" to execute if false
1 # Push a truthy value to the stack
#1 # A function that just repeatedly pushes true
: # While the top of the stack is true. Thus, loop forever
? # If a, than b, else c
<SPACE> # Used to ensure the function qualifies as a quine.
ATaco
Posted 2020-01-26T04:34:22.757
Reputation: 7 898
2
ATaco
Posted 2020-01-26T04:34:22.757
Reputation: 7 898
2
Expired Data
Posted 2020-01-26T04:34:22.757
Reputation: 3 129
20 bytes, though I'm not sure if exceeding the recursion limit counts as infinite. At the very least, you can get rid of the trailing semicolon – Jo King – 2020-01-30T13:04:12.923
@JoKing Yeah I thought about that but I don't think that really counts, since it's bounded by the size of the stack, thanks for the -1, I did think about something similar with f=x=>x=='f='+f?x:eval("for(;;);") but it's 33 bytes – Expired Data – 2020-01-30T13:22:06.560
Another 33 f=x=>eval(\while(x!='f='+f);`)||x` – Expired Data – 2020-01-30T13:26:47.893
1@PostRockGarfHunter Strengthened the requirements. Now this challenge differs from a cat program. – Dannyu NDos – 2020-01-26T04:54:30.330
8This is why we sandbox. – Post Rock Garf Hunter – 2020-01-26T05:00:35.680
Here's a similar question, hopefully the answers can provide inspiration for others! https://codegolf.stackexchange.com/questions/11370
– Josh – 2020-01-27T21:53:19.000