ter = 1 + 3
```
]

---
# 1. Vals are evaluated only once

.fifty-two-left[
```scala
import java.time.Instant

val nowSeconds = Instant.now().getEpochSecond
// nowSeconds: Long = 1616594266L
```
]


<br><br><br><br><br><br><br>

.fifty-two-left[
```scala
nowSeconds
// res: Long = 1616594266L

nowSeconds
// res: Long = 1616594266L
```
]

---
# 2. Defs

.forty-seven-left[
```scala mdoc
def greeting(): Unit =
  println("Hello")
```
]

---
# 2. Defs are evaluated when called

.forty-seven-left[
```scala mdoc:res