Rust — Operators

Arithmetic

let a = 10;
let b = 3;

a + b     // 13
a - b     // 7
a * b     // 30
a / b     // 3    ← INTEGER division (truncates) when both are ints!
a % b     // 1    remainder

The / surprise: 10 / 3 gives 3, not 3.33. Floats divide properly only when an operand is a float:

10.0 / 3.0     // 3.3333333333333335

No ** power operator — use methods:

2i32.pow(8);        // 256
10f64.sqrt();

Comparison

5 == 5      // true   (values must be SAME type to even compile)
"abc" < "abd"   // true, lexicographic

Unlike JavaScript there's no == vs === split and no coercion — "5" == 5 is a compile error, not a surprise.

Logical

let logged_in = true;
let is_admin = false;

logged_in && is_admin     // AND
logged_in || is_admin     // OR
!logged_in                // NOT

Short-circuiting works as expected:

// second call skipped if first fails:
if connected() && send_data() { … }

Compound assignment

let mut score = 10;
score += 5;    // 15
score -= 3;    // 12
score *= 2;    // 24
score /= 4;    // 6
score %= 4;    // 2

Note: += requires the variable be mut.

No increment operator

Rust has no ++ or --:

i += 1;    // the idiomatic way

Truthiness does NOT exist

Conditions must be genuine booleans:

let count = 0;

if count { … }              // ❌ error: expected bool, found integer
if count != 0 { … }         // ✓ explicit
if !name.is_empty() { … }   // ✓

Empty string/zero collections are not falsy in Rust — this removes a whole class of subtle bugs other languages breed.

Operator precedence quick reference

highest:  *  /  %
          +  -
          <<  >>
          &  ^  |
          ==  !=  <  >  <=  >=
          &&
lowest:   ||

Parenthesize anything non-trivial — free clarity.

Mini Practice

1. Predict then verify 17 / 5, -17 / 5, 17 % -5.
2. Fix if items.len() { … } — explain the compiler message.
3. Build a login check with && combining three bools.
4. Use powi/pow for squares and cubes of floats.
5. Show that "5" == 5 doesn't compile; compare after parsing instead.

Next: booleans → (already written)