M-ary PSK code from M-ary QAM code

Hi all.

My professor has handed a code for the M-ary QAM

% function for realizing M-QAM modulation %
function simSerMQAM = mQAM(M, EsN0dB)
j = sqrt(-1); % imaginary unit %
numSim = 7*10^5; % number of simulation symbols %
k = sqrt(1/((2/3)*(M-1))); % factor for normalizing energy %
m = [1:sqrt(M)/2]; % alphabets %
alphaMqam = [-(2*m-1) 2*m-1];
errSymsQAM = zeros(1, length(EsN0dB));
for ii = 1:length(EsN0dB)
infoSyms = randsrc(1,numSim,alphaMqam) + j*randsrc(1,numSim,alphaMqam);
infoSymsQAM = k*infoSyms; % normalization of energy to 1 %
noise = 1/sqrt(2)*[randn(1,numSim) + j*randn(1,numSim)]; % white guassian noise, 0dB

tranSymsQAM = infoSymsQAM + 10^(-EsN0dB(ii)/20)*noise; % additive white gaussian noise %
% demodulation %
tranSymsRe = real(tranSymsQAM)/k; % real part %
tranSymsIm = imag(tranSymsQAM)/k; % imaginary part %
% rounding to the nearest alphabet %
recSymsRe = 2*floor(tranSymsRe/2)+1;
recSymsRe(find(recSymsRe >max(alphaMqam))) = max(alphaMqam);
recSymsRe(find(recSymsRe <min(alphaMqam))) = min(alphaMqam);
% rounding to the nearest alphabet %
recSymsIm = 2*floor(tranSymsIm/2)+1;
recSymsIm(find(recSymsIm >max(alphaMqam))) = max(alphaMqam);
recSymsIm(find(recSymsIm <min(alphaMqam))) = min(alphaMqam);
demoSyms = recSymsRe + j*recSymsIm;
% counting the number of symbol errors %
errSymsQAM(ii) = size(find([infoSyms - demoSyms]),2);
end
simSerMQAM = errSymsQAM/numSim;
end

%To run in command window 
simSerMQAM = errSymsQAM/numSim;
end

and wants up to produce a M-ary PSK code based on that. Problem is, neither I nor anyone from my peer group can understand this code and I have been wracking my brains on this without knowing what to do. I am hoping that someone would be kind enough to shed light on this and what it does because I don't know what to do with it.