g | x | w | all

Bytes	Lang	Time	Link
2077	JavaScript Node.js and brainfuck	240807T225508Z	Andrew B
015	05AB1E and Y	230206T141004Z	Kevin Cr
039	Vyxal + 05AB1E	231122T002454Z	Fmbalbue
018	Clip and Fission	230806T223346Z	jimmy230
243	Minecraft Function and C	230806T202130Z	LostXOR
119	C and Python	230212T181134Z	pan
035	dc and Fission	230212T185234Z	Conor O&
119	C/C++	230207T123017Z	l4m2
095	Python 3.8 prerelease + JavaScript Node.js	230207T152735Z	Jakque
041	PHP Perl 4 or 5	230207T101611Z	Kaddath
068	JavaScript	230207T055451Z	tsh
107	Python	230207T102713Z	tsh
150	Python + JavascriptNode.js	230206T175824Z	M Virts
175	Java and Whitespace	230206T154043Z	Kevin Cr
049	Python + ><>	230206T134701Z	mousetai

JavaScript (Node.js) and brainfuck, 2077 bytes

/*++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++.>++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++.>+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++.>+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++.>++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++.>++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++.>+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++.>+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++.>+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++.>>.++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++>.++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++>.+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++>.++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++>.+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++>.+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++>.+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++>.++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++>.+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++>.++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++*/eval("console\56log('JavaScript')")//)")'kcufniarb'(gol65\elosnoc"(lave

Try it online - JavaScript

Try it online - brainfuck

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.

05AB1E and Y, 15 bytes

"Y"gxg"E1BA50"R

Try it online in 05AB1E.
Try it online in Y (you'll have to copy-paste "Y"gxg"E1BA50"R into the Code-block, and click on the 'timeout run'-button).
Try it reversed in 05AB1E.
Try it reversed in Y (again, by copy-pasting 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

Vyxal + 05AB1E, 39 bytes

"‛₴ŀ,Q,`E1BA50``"i0"laxyV"}"05AB1E"0i0`

Clip and Fission, 18 bytes

"Clip";"noissiF"L+

Try it online in Fission!

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 and Fission, 25 bytes

"GolfScript"K}K"noissiF"L

Try it online in GolfScript!

Try it online in Fission!

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.

Minecraft Function and C, 243 bytes

#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:

C
C Reversed

(Minecraft Function not available on TIO)

C and Python, 163 119 bytes

p=0//1;print("Python")#//#
#define p;main(){puts("C");}//#
p
#//};)"nohtyP"(stup{)(niam;p enifed#
#//#)"C"(tnirp;1//0=p

Try it online!

`warning`-less & C`99` 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#

Try it online!

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".

dc and Fission, 35 bytes

[dc]P[;"cd"R"Fission";][[P]noissiF[

Try it online! dc in dc.

Try it online! Fission in Fission.

Try it online! Fission in dc reversed.

Try it online! dc in Fission reversed.

Explanations

dc → `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 → `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

dc reversed → `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

Fission reversed → `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

C/C++, 119 bytes

#include<stdio.h>//
int main(){puts(sizeof!0-1?"C":"C++");}//};)"++C+0\C0"+0!foezis(stup{)(niam tni
//>h.oidts<edulcni#

Try it online!

Reference

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#

Try it online!

~~Not that elegant due to #ifdef but resolving it also save bytes~~ done

Python 3.8 (pre-release) + JavaScript (Node.js), 95 bytes

1//print("Python")#1//)"nohtyP"(gol.elosnoc
console.log("JavaScript")//1#)"tpircSavaJ"(tnirp//1

Try it online! (Python)

1//print("Python")#1//)"nohtyP"(gol.elosnoc
console.log("JavaScript")//1#)"tpircSavaJ"(tnirp//1

Try it online! (JavaScript)

The python programs error after printing

PHP Perl 4 or 5, 45 43 41 bytes

print-true?php:perl;#;php:lrep?eurt-tnirp

Try it online PHP

Try it online Perl

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

JavaScript, HTML, 68 bytes

HTML JavaScript

Normal

	HTML	JavaScript
Normal	<!---->HTML<!--!<tpircSavaJ>-- alert`JavaScript`//`LMTH`trela <!--!<	<!---->HTML<!--!<tpircSavaJ>-- alert`JavaScript`//`LMTH`trela <!--!<
Reversed	<!--!< alert`HTML`//`tpircSavaJ`trela -->JavaScript<!--!<LMTH>----!<	<!--!< alert`HTML`//`tpircSavaJ`trela -->JavaScript<!--!<LMTH>----!<

<!---->HTML<!--!<tpircSavaJ>--
alert`JavaScript`//`LMTH`trela
<!--!<

<!---->HTML<!--!<tpircSavaJ>--
alert`JavaScript`//`LMTH`trela
<!--!<

Reversed

<!--!<
alert`HTML`//`tpircSavaJ`trela
-->JavaScript<!--!<LMTH>----!<

<!--!<
alert`HTML`//`tpircSavaJ`trela
-->JavaScript<!--!<LMTH>----!<

JavaScript is a strange language that support 5 kinds of comment and 5 kinds of link breaks.

Comment:

Multi line comment /* ... */ Ref
Single line comment // ... Ref
Hashbang comment #! ... Ref
- Must at the beginning of source code
- Some script host support an extra BOM in front of hashbang
Single line HTML open comment <!-- ... Ref
Single line HTML close comment --> ... Ref

Line breaks: Ref

<LF>
<CR>
<LS>
<PS>
<CR> <LF>

Python, JavaScript (Node.js), 107 bytes

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 + Javascript(Node.js) 150 bytes

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"]),'\"'

Java and Whitespace, 175 bytes

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.

Python + ><>, 49 bytes

#o<"><>"
print("python")#)"><>"(tnirp
"nohtyp"<o#

Try it:

JavaScript (Node.js) and brainfuck, 2077 bytes

05AB1E and Y, 15 bytes

Vyxal + 05AB1E, 39 bytes

Clip and Fission, 18 bytes

GolfScript and Fission, 25 bytes

Minecraft Function and C, 243 bytes

C and Python, 163 119 bytes

warning-less & C99 compliant version, 235 bytes

dc and Fission, 35 bytes

Explanations

dc → dc

Fission → Fission

dc reversed → Fission

Fission reversed → dc

C/C++, 119 bytes

Python 3.8 (pre-release) + JavaScript (Node.js), 95 bytes

PHP Perl 4 or 5, 45 43 41 bytes

JavaScript, HTML, 68 bytes

Python, JavaScript (Node.js), 107 bytes

Python + Javascript(Node.js) 150 bytes

Java and Whitespace, 175 bytes

Python + ><>, 49 bytes

`warning`-less & C`99` compliant version, 235 bytes

dc → `dc`

Fission → `Fission`

dc reversed → `Fission`

Fission reversed → `dc`