Last night I was looking for the Radiation Hardened Quine challenge, but I couldn't find it. Turns out no one has asked it yet! So here it is:
Your task is to make a quine, that is a non-empty computer program that prints it's own source without reading it. In addition if you remove any one byte from your original program the new program should print the source of your original program.
This is code-golf so answers are scored in bytes with fewer bytes being better.
<<H~Kla}\`q%2l}}ss2"<\
<<H~Kla}\`q%2l}}ss2"<\
I did this in Gol><> rather than ><> because the former has the handy K operator that copies the top n items on the stack, which makes duplicating the clean copy of the source code easier.
This works by having two copies of the executing code, and redirecting to the second one if the first is damaged. This fails when the last \ or the middle newline is removed, both of which are compensated for later.
<< Redirect left
<\ Switch to other source code if this line is irradiated
" Push source with wrapping string literal
ss2 Push quote
}} Move "< to end
q%2l If the length of the stack is not right
\` Push an extra \
} Move the \ to the end
a Newline
Kl Duplicate the stack
~ Pop the extra newline
H Halt and print stack
