"Hello, World!" (Robbers' thread)

Question

This is the robbers' thread. The cops' thread is here.

Your challenge is to take an uncracked submission from the cops' thread and find, for what input or inputs, the program will print Hello, World! and a newline. Capitalization, spacing, and punctuation must be exact.

Please comment on the cop's submission when you've cracked their code.

Answer 1

TeX, by A Gold Man

Original source:

\read16to\x\message{Hello, World!}\bye

This already prints Hello, World!, but the newline is missing. The input is just placed in \x which is never used. In order to be able to modify the output, I guess we need to do some preparations (like, "lay a trap") before calling this code, so \x is actually expanded. It can be done when invoked like this (assuming the original source is in x.tex in the current directory):

tex '\def\vfill{\x}\input./x'

This first redefines \vfill (which is part of the expansion of \bye) to expand to our \x, so now we can provide some input printing the missing newline:

\newlinechar=`@\message{@}

This sets the character used for newlines in \message to @ and immediately uses it.

---

This whole thing modifies the environment the original program will run in, so if there are any objections to this method, I'll retract it.

Answer 2

Brainfuck by 2EZ 4RTZ

Correct input: Gdkkn+\x1fVnqkc \x09\xff, where \xHH indicates non-ASCII-printable hex character.

Explanation:

You just take the character codes of "Hello, World!\n" and subract one from each value. The last character \xff (255) causes the program to exit after you add one (since the 255+1 overflows to 0 and the loop exits).

Answer 3

><> by Not a tree

This was an EPIC puzzle! I loved it!

Example solution:

TIHANICWHITEOCPSEARK

Wish I could upvote Not a tree's post three more times.

Answer 4

Perl 5, by Chris

Original code:

eval<>;END{print$x='x'}

Input:

our $x;package X;require Tie::Scalar;@ISA=qw(Tie::Scalar);sub TIESCALAR{my$v;return bless\$v,'X';}sub STORE{}sub FETCH{return "Hello, World!\n"}tie $x,'X';

I'm not sure this is the intended solution. It works by changing the behavior of $x using a tie. The tie here is very simple, ignoring any STORE access and returning our desired output for any FETCH.

Try it online!

Answer 5

JavaScript (ES6), Voile

Input:

!(v.call=()=>true)||"()=>`Hello, World!\n`"

Cop code:

const e=eval,p=''.split,c=''.slice,v=[].every,f=s=>(t=c.call(s),typeof s=='string'&&t.length<81&&v.call(p.call(t,`\n`),l=>l.length<3)&&e(t)(t))

Try it online

This overwrites the v.call() method to always return true, but that part of the input is falsified and discarded for the string part which passes the string type check and length check, and eval's to the desired output Hello, World!\n.

If Birjolaxew's crack is not accepted, maybe this one will.