Logical indicator in objective function

How to write a logical indicator as part of objective function? The objective function is as below

sum (a*(x(i) - x(i-1) + l(i) - g(i)))

a is 1 when

x(i) - x(i-1) + l(i) - g(i) > 0

otherwise a is 0. The decision variable is x.

Thanks!

Answer 1

[Walter Roberson]

t = diff(x) + l - g;
objective = sum( t(t>0) )

No loop needed.