Dr. @
Winstead, I have tried implementing the symbol-flipping algorithm over GF(4) for a given parity check matrix in octave. One approach I tried was checking the syndrome for each symbol in the received code word. Another one is by considering hamming distance... min hamming distance between the received vector and valid codewords resulting in the corrected codeword.
I was not able to commit the files in our LDPCsimulaiton repo. Hence, I uploaded them in the below repo of mine. I have not added a README file yet, which I will do shortly. There are some issues in the code or algorithm that I might need to discuss with you tomorrow.
#^https://github.com/zinniamowri/symbol_flipping_GF4