How to escape control characters?

[cy via Digitalmars-d-learn]

On Thursday, 31 March 2016 at 03:23:52 UTC, Seb wrote:
> http://dlang.org/spec/lex.html#WysiwygString
>
> r"ab\n" or `ab\n`

Yes I know. But I mean like,

string a = r"ab\n";
writeln(escape(a)); // => ab\n