I'm not sure wha't is the function you want to take the inetgral from. I guess it's Dirac or as you said delta, if you want to perform a symbolic inegral you have to define a symbol first
syms x
y=int(dirac(x))
subs(y,.999)-subs(y,0)
Which gives you 1 anyway! Hope that wouls solve the problem! Good luck!