Imperative vs Reactive

in an imperative programming setting:

• 𝐴 = 𝐵 + 𝐶 would mean that 𝐴 is being assigned the result of 𝐵 + 𝐶 in the instant the expression is evaluated, and later, the values of 𝐵 and 𝐶 can be changed with no effect on the value of 𝐴

in reactive programming:

• the value of 𝐴 is automatically updated whenever the values of 𝐵 or 𝐶 change, without the program having to re-execute the statement 𝐴 = 𝐵 + 𝐶 to determine the presently assigned value of 𝐴