Generic fuzzy operations help

hi all

if i had something like

 x = -10:0.1:10;
 f1 = trapmf(x, [-2 0 0 3]); 
 f2 = trapmf(x, [1 3 3 4]);

this gives me a 1x201 matrix for x, f1, and f2.

I'm trying to make a generic coding (not the built-in fuzarith function) that can solve fuzz (add subtract divide and multiply)

my main issue is that for fuzzy operation, I have to work with the function values of f1 and f2, not x, which is different for every function i put in.

for example, to fuzzy add, I have to find the x values of where f1 and f2 are at some arbitrary point, let's say 0.5, and get the x-values of each f1(0.5) and f2(0.5).

but then this doesn't work because f1 and f2 do not necessarily have a value of 0.5 at any x. then I tried to work with indexes but I ran into a problem of f1 and f2 having different number of non-zero values to work with..

what would be a possible approach?

any hints/comments will be highly appreciated. thanks.