Imperative vs Declarative

Declarative programs we are describing what to do, rather than how to do it.

Imperative

let mut sum = 0;
for i in 1..11 {
    sum += i;
}
println!("{}", sum);

Declarative

Imperative

let mut sum = 0;
for i in 1..11 {
    sum += i;
}
println!("{}", sum);

Declarative

Declarative programs we are describing what to do, rather than how to do it.

println!("{}", (1..11).fold(0, |a, b| a + b));