MATLAB: Particularly strange bug using the eval function

bad ideabugevalgammaMATLABmatlab functionnot a bug

In the MWE below, I define a bunch of parameters using an eval command. I know that the experts recommend against using eval, as in this thread, but I don't really see an alternative in this instance. I also know that MATHWORKS would prefer me not to define variables that clash with their own builtins. However, the code still should work properly, but doesn't in this example.
The class for rho is correctly defined as double. But the fourth last line returns an error, as does the second last line. In both cases the code still thinks gamma is matlab's built-in function. Yet the third last line indicates that gamma is correctly defined as 0.6. Note that if I remove the first line of the code, and thus run the code in the base workspace, everything works as expected.
Could somebody please explain a) what's causing this bug and b) a simple alternative to my use of the eval function?
function nothing 
rhoY			= 0.8; 
phiY			= 0.8; 
gammaY			= 0.6; 
etaY			= 0.05;
muY				= .5;  
ecLetter		= 'Y';		
Params			= {'phi','rho','eta','gamma','mu'};
nParam			= numel(Params);
for ii=1:nParam;
	thisParam		= Params{ii};
	eval([thisParam '=' thisParam ecLetter ';']);
end;
%This kludge fixes the problem
tmp=gamma;
gamma=tmp;
class(rho)
class(gamma)
gamma
3*gamma
keyboard;

Best Answer

I reproduced the issue you report on R2018b, Win10.
I noticed that if
  • I put a breakpoint at the line "class(gamma)"
  • run the function, nothing
  • execute "class(gamma)" by select, right click, Evaluate Selection
  • "class(gamma)" returns the result that you expect
The issue has something to do with the Just-In-Time (JIT) accelerator, I think. You could report it as a bug. (However, DB's answer make me believe they already knows about a bunch of similar cases.)
IMO:
  • Experiments with this kind of code is a waste of time. However, the group working on the JIT should be interested in your observation.
  • "but I don't really see an alternative in this instance." Describe "this instance" and someone here might come up with a better alternative.
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