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RUNIX COPS AND ROBBERS CMDS CODE

But since we have it immediately after a \E, it can't be immediately after a \. (+ is not part of any legal group structure, and will generate a compile-time error ("Incomplete group structure" and/or "The preceding token is not quantifiable" / "quantifier does not follow a repeatable item") anywhere other than: And if we weren't in one, but are preceded by a \, then it will be treated as a literal \E, and we'll still be guaranteed not to be inside a \Q. By starting this one with \E, we break out of such a sequence if we were in one.

If we're inside a ' string, then the first ' will close it, with the remaining ' being commented out by the #, leaving $ by itself.Īny string not containing \E would be legal inside a \Q.

If we're inside a " string, then the first " will close it, which is then followed by the legal '#' string.

If we're embedded in a comment, our entire first line will be commented out, leaivng a lone $, which is illegal.

If there's no leading code, then the comment removes the rest of the first line.

The idea is since $ is not a legal function, it cannot appear outside of strings. However, that kind of defeats the spirit of the question as well IMO, so let's assume that we're actually in some arbitrary expression: #"'#'

So, you could prefix any program with TRUE-a valid expression-after which anythign afterwards would be undefined behaviour. Technically, knight programs aren't allowed to contain anything outside of \r, \n, \t, or - ~, so you could just submit for a one byte solution.Īdditionally, each knight program is exactly a single expression handling things after that experssion is up to the implementation. (The definition of this "trailing section" is language-dependent, but generally means any text after the parser has entirely stopped reading the script).īut this can be embedded into the larger program """ Make sure to make a note of that in your answer. For such languages, you may submit a solution that can appear only in such a trailing section. Bash, Batch, Perl) allow arbitrary binary data to be appended to a program without affecting validity (e.g. one that doesn't produce any errors) that contains the proposed substring. More specifically, you should provide a link to TIO or equivalent demonstrating a legal program (i.e. Dispute incorrect solutions in the comments.You should explain why your string is illegal (why it cannot appear anywhere in a legal program).Shortest illegal string for each language wins.The error does not have to be the same across programs - one embedding of your string might cause a syntax error, while another might cause a runtime error.

RUNIX COPS AND ROBBERS CMDS CODE

The compiler/interpreter/runtime must give an error when given any source code that contains your string as a substring.

Every individual character in your submission must be admissible in a legal program that is, you can't just use a character which is always rejected.

strings which fail solely due to character decoding errors are not allowed). UTF-8), your string must also be correctly encoded (i.e.

If your programming language requires a specific encoding (e.g.

passing a flag to convert warnings into errors). You cannot pass some weird flag to your compiler to get a specific result (e.g. Only standard compiler/interpreter/runtime options are permitted.Your program may be specific to a particular version or implementation of your language's compiler/interpreter/runtime environment.That includes comments, strings, or other "non-executable" parts.

The challenge is to find a string of characters that cannot appear in any legal program in your programming language of choice.