Write a polyglot in two languages that when run, outputs the name of the language it is run in. Additionally, this program must also output the other language's name if the source code is reversed
Program ABC in language foo outputs foo. ABC in language bar outputs bar. CBA in language foo outputs bar, and CBA in language bar outputs foo.
This is code-golf, so the shortest code wins
| HTML | JavaScript | |
|---|---|---|
| Normal | |
|
| Reversed | |
|
JavaScript is a strange language that support 5 kinds of comment and 5 kinds of link breaks.
Comment:
/* ... */ Ref// ... Ref#! ... Ref
<!-- ... Ref--> ... RefLine breaks: Ref
<LF><CR><LS><PS><CR> <LF> 
#o<"><>"
print("python")#)"><>"(tnirp
"nohtyp"<o#
Try it:
v->"Java"//"ecapsetihW">-vSSTTN
SSTTTN
SSTTSTN
SSSTSTSN
SSSTTSTN
SSTTN
SSSTTTSN
SSSTTN
SSSTSN
SSTTTTTN
N
SSN
SSSTTSSTTSN
TSSSTN
SSN
SN
N
N
N
SN
SSN
TSSSTN
SSSSSTTSSSN
SSN
N
STTSTTSSN
TSSSN
STTSTSSSN
TSSS
Above, the spaces, tabs, and newlines are indicated with S; T; and N respectively for readability only. The TIO-links below contain the actual spaces/tabs/newlines.
Explanation:
In Java:
v-> // Method with empty unused parameter & String return-type
"Java" // Return "Java"
//"ecapsetihW">-v // No-op comment
// No-op spaces/tabs/newlines
In Java reversed:
// No-op spaces/tabs/newlines
v-> // Method with empty unused parameter & String return-type
"Whitespace" // Return "Whitespace"
//"avaJ">-v // No-op comment
In Whitespace:
v->"Java"//"ecapsetihW">-v // No-ops
SSTTN // Push -1 (e)
SSTTTN // Push -3 (c)
SSTTSTN // Push -5 (a)
SSSTSTSN // Push 10 (p)
SSSTTSTN // Push 13 (s)
SSTTN // Push -1 (e)
SSSTTTSN // Push 14 (t)
SSSTTN // Push 3 (i)
SSSTSN // Push 2 (h)
SSTTTTTN // Push -15 (W)
NSSN // Create Label LOOP
SSSTTSSTTSN // Push 102
TSSS // Add the top two integers together
// (which will implicitly stop the program with an error if
// there is just a single value on the stack)
TNSS // Print the top as character to STDOUT
NSNN // Jump to Label LOOP
NNSNSSNTSSSTNSSSSSTTSSSNSSNNSTTSTTSSNTSSSNSTTSTSSSNTSSS
// No-op whitespaces
In Whitespace reversed:
SSSTN // Push 1 (a)
SSSTSTTSN // Push 22 (v)
SSSTN // Push 1 (a)
SSTTSTTSN // Push -22 (J)
NSSN // Create Label LOOP
SSSTTSSSSSN // Push 96
TSSS // Add the top two integers together
// (which will implicitly stop the program with an error if
// there is just a single value on the stack)
TNSS // Print the top as character to STDOUT
NSNN // Jump to Label LOOP
NNSNSSNTSSSTNSTTSSTTSSSNSSNNTTTTTSSNSTSSSNTTSSSNSTTTSSSNTTSSNTSTTSSSNSTSTSSSNTSTTSSNTTTSSNTTSS
// No-op whitespaces
v->"Whitespace"//"avaJ">-v // No-ops
The constants 102 and 96 are generated by this Java program based on this Whitespace tip of mine.
"Y"gxg"E1BA50"R
"Y"gxg"E1BA50"R into the Code-block, and click on the 'timeout run'-button).R"05AB1E"gxg"Y" manually).Explanation:
In 05AB1E:
"Y" # Push string "Y"
# STACK: "Y"
g # Pop and push its length
# STACK: 1
x # Double it (without popping)
# STACK: 1,2
g # Pop and push its length
# STACK: 1,1
"E1BA50" # Push string "E1BA50"
# STACK: 1,1,"E1BA50"
R # Reverse it
# STACK: 1,1,"05AB1E"
# (after which the top of the stack is output implicitly)
In 05AB1E reversed:
R # Reverse (without input, it'll push an empty string)
# STACK: ""
"05AB1E" # Push string "05AB1E"
# STACK: "","05AB1E"
g # Pop and push its length
# STACK: "",6
x # Double it (without popping)
# STACK: "",6,12
g # Pop and push its length
# STACK: "",6,2
"Y" # Push string "Y"
# STACK: "",6,2,"Y"
# (after which the top of the stack is output implicitly)
In Y:
"Y" # Push string "Y"
g # Pop and print it
x # Stop the program
g"E1BA50"R # No-ops
In Y reversed:
R # No-op character
"05AB1E" # Push string "05AB1E"
g # Pop and print it
x # Stop the program
g"Y" # No-ops
05AB1E, not E1BA50.
\$\endgroup\$
Commented
Nov 22, 2023 at 0:45
Uses the differences between javascript objects and python dicts to change code passed to eval in both languages. Uses both quoting styles with escaping to evaluate different code when reversed
"'\",)]'0'[}')'\nohtyP'\(gol.elosnoc':0,')'\tpircsavaJ'\(tnirp':'0'{(lave,'",eval({"0":"print(\"Python\")",0:"console.log(\"Javascript\")"}["0"]),'\"'
"'\",)]0[}'nohtyP':'0','tpircsavaJ':0{(tnirp,'",print({0:"Python","0":"Javascript"}[0]),'\"'
\$\endgroup\$
#include<stdio.h>//
int main(){puts(sizeof!0-1?"C":"C++");}//};)"++C+0\C0"+0!foezis(stup{)(niam tni
//>h.oidts<edulcni#
Old: C/C++, 167 bytes
#include<stdio.h>//
int main(){puts("C"//
#ifdef __cplusplus//
"++"//
#endif//
);}//};)
//fidne#
//"++"
//sulpsulpc__ fednfi#
//"C"(stup{)(niam tni
//>h.oidts<edulcni#
Not that elegant due to done#ifdef but resolving it also save bytes
print-true?php:perl;#;php:lrep?eurt-tnirp
A simple take at it, I assumed it was not mandatory to specify the Perl version as it is not a polyglot between different versions of perl (though I could do one). Works in Perl 4 or 5
Takes advantage of the fact that PHP converts true to 1 for numerical operations while Perl 4/5 ignores it
EDIT: saved 2 bytes by removing 1, -true is enough (with swaped languages names)
EDIT 2: thanks to Neil for saving another 2 bytes removing the spaces
p=0//1;print("Python")#//#
#define p;main(){puts("C");}//#
p
#//};)"nohtyP"(stup{)(niam;p enifed#
#//#)"C"(tnirp;1//0=p
warning-less & C99 compliant version, 235 bytes
#include<stdio.h>//#
#define p int main(void){puts("C");}//#
#if 0//fidne#
print("Python");p=0//1#//#
#endif//0 fi#
p
#if 0//fidne#
#//#1//0=p;)"C"(tnirp
#endif//0 fi#
#//};)"nohtyP"(stup{)diov(niam tni p enifed#
#//>h.oidts<edulcni#
Turns out, since C99, main() does implicitly return 0 which indicates successful termination.
A single # (with optional whitespaces and/or comments after it) followed by a new line is also allowed; The standard calls it "Null directive".
#include <stdio.h> for puts() and the int type specifier for main(). Since it's C, the empty parameter list must also be (void), and you must explicitly return 0 (or EXIT_SUCCESS by also #including <stdlib.h>. Some compilers might not accept #), #//, )#. I had a version that (ab)used the #line directive and some extra Python boilerplate to workaround this.
\$\endgroup\$
1//print("Python")#1//)"nohtyP"(gol.elosnoc
console.log("JavaScript")//1#)"tpircSavaJ"(tnirp//1
1//print("Python")#1//)"nohtyP"(gol.elosnoc
console.log("JavaScript")//1#)"tpircSavaJ"(tnirp//1
The python programs error after printing
[dc]P[;"cd"R"Fission";][[P]noissiF[
Try it online! Fission in Fission.
Try it online! Fission in dc reversed.
Try it online! dc in Fission reversed.
dc[dc]P[;"cd"R"Fission";][[P]noissiF[
[dc] push the string "dc"
P print without newline
[;"cd"R"Fission";] push the string (psuedo comment)
[ push the rest of the program as string (ditto)
Fission[dc]P[;"cd"R"Fission";][[P]noissiF[
R start an atom going right
"Fission" print "Fission" and set the atom's mass to 7
; destroy the atom
Fission[Fission]P[[];"noissiF"R"dc";[P]cd[
[ ] push the string "Fission"
P print without newline
[ push the rest of the program as string (psuedo comment)
note that dc's [strings] nest
and also doesn't complain with an unterminated string
dc[Fission]P[[];"noissiF"R"dc";[P]cd[
R start an atom going right
"dc" print "dc" and set the atom's mass to 2
; destroy the atom
#include <stdio.h>//a fednu#
#define w int main(){printf("C");}//a fednu#
w
#undef a//>h.oidts< edulcni#
#undef a//};)"noitcnuF tfarceniM"(ftnirp{)(niam tni w enifed#
#if 0//fidne#
tellraw @a "Minecraft Function"#
#"C" a@ warllet
#endif//0 fi#
The C code is hidden behind preprocessor directives, which are interpreted as comments in the Minecraft function. The Minecraft code is hidden with #if 0 and #endif which is completely skipped by the compiler.
The code is written symmetrically with appropriate comments to comment out the reversed version. #undef a// (a comment in Minecraft and a no-op in C) is used to hide the reversed code.
The w, which is interpreted in C as int main(){printf("C");}, is also a valid Minecraft command. It has the wrong number of arguments, which causes a silent error, but the rest of the function still runs.
Try It Online:
(Minecraft Function not available on TIO)
00000000: 2321 2f2f e280 a863 6f6e 736f 6c65 2e6c #!//...console.l
00000010: 6f67 2822 4a61 7661 5363 7269 7074 2229 og("JavaScript")
00000020: 2f2f 2922 6e6f 6874 7950 2228 676f 6c2e //)"nohtyP"(gol.
00000030: 656c 6f73 6e6f 63e2 80a8 3b60 230a 7072 elosnoc...;`#.pr
00000040: 696e 7428 2250 7974 686f 6e22 2923 2922 int("Python")#)"
00000050: 7470 6972 6353 6176 614a 2228 746e 6972 tpircSavaJ"(tnir
00000060: 700a 2360 e280 a82f 2f21 23 p.#`...//!#
No TIO link available...
All you need is comment out whatever you don't want...
python -c 'open("2.js","w",encoding="utf-8").write(open("1.js",encoding="utf-8").read()[::-1])'. And execute it using node 2.js. Let me know any errors you will get after execute these commands.
\$\endgroup\$
v12.22.9 I'm using. As this program does not use any non-standard node features, it should work for any node version newer than 12.22.9.
\$\endgroup\$
cat tsh_poly.xxd | xxd -r > tsh_poly.pyjs to create the file for testing.
\$\endgroup\$
"Clip";"noissiF"L+
Try it online in Fission reversed!
No online link for Clip.
In Clip, most things after the first entity and its parameters recursively don't matter. (Some operators also wait for input, but not in this case.) Strings takes no parameters. L is an empty list. + is for concatenation.
In Fission, L emits an atom to the left and ; destroys the atom. Strings in double quotes on the path of the atom are printed. It wraps around on the edges like most 2D languages.
"GolfScript"K}K"noissiF"L
Try it online in GolfScript reversed!
Try it online in Fission reversed!
In GolfScript, K is a no-op and } is a super comment.
In Fission, K works like ; but also does something else that doesn't matter. Using ; here would break GolfScript.
/*++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++.>++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++.>+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++.>+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++.>++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++.>++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++.>+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++.>+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++.>+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++.>>.++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++>.++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++>.+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++>.++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++>.+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++>.+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++>.+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++>.++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++>.+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++>.++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++*/eval("console\56log('JavaScript')")//)")'kcufniarb'(gol65\elosnoc"(lave
Try it online - JavaScript (reversed)
Try it online - brainfuck (reversed)
Explanation:
In JavaScript, the main code looks like this - an eval statement with the bf code on the left inside /* */, and the reversed JS code on the right to the right of //
/* brainfuck code */ eval("console\56log('JavaScript')") //reversed JavaScript
Note that if I used . or [] to get the log property of console, then those characters would affect brainfuck, so I used eval, and replaced the . with it's octal escape sequence.
On the brainfuck side, the code looks like this (when broken onto separate lines):
++++++++++++++++++++++++++++++++++++++++++++++++.> print 'b'
+++++++++++++++++++++++++++++++++++++++++++++++++++.> print 'r'
+++++++++++++++++++++++++++++++++++++++++++++.> print 'a'
>.+++++++++++++++++++++++++++++++++++++++++++++ print ascii(0)
>.+++++++++++++++++++++++++++++++++++++++++++++++++++ print ascii(0)
>.++++++++++++++++++++++++++++++++++++++++++++++++ print ascii(0)
A purist may claim that I've cheated because I'm outputting ascii zeros, however the effect on TIO is that these chars don't appear or do anything to the output.
I couldn't use [], because when reversed it becomes ][ which are mismatched and will give rise to an error.
