A self-recognizing function

Recently I have been thinking about recursive sets. These are sets that have a computable characteristic function. A standard example of a set that is not recursive is the set of programs that recognize themselves. Earlier I wrote about quines, which are programs that print their own source code. The self-referencing method used in the Python quine allowed me to write the following function that recognizes its own source code (modulo Python string equivalence, e.g., 'a' == '''a'''):

lambda x, s = 'lambda x, s = %r : s%%s == x' : s%s == x

You can try this out with:

ss = "lambda x, s = 'lambda x, s = %r : s%%s == x' : s%s == x"
eval(ss)(ss)