deanwampler

scala> case class Person(name: String, age: Int):
     |   def this(name:String) = this(name, 18)
// defined case class Person

scala> Person("Dean", 100)
val res2: Person = Person(Dean,100)

scala> Person("Dean")
1 |Person("Dean")
  |^^^^^^^^^^^^^^

deanwampler

scala> class JavaPerson(val name: String, val age: Int):
     |   def this(name:String) = this(name, 18)
// defined class JavaPerson
     
scala> JavaPerson("Dean", 100)
     | JavaPerson("Dean")
     |
val res0: JavaPerson = JavaPerson@6684da5b
val res1: JavaPerson = JavaPerson@34b156ba

deanwampler

import scala.compiletime.ops.int.*

// Only allowed values are Min <= N <= Max.
type Bounded[MIN <: Int, MAX <: Int] <: Int = MAX match 
  case MIN => MIN
  case ? => MAX | Bounded[MIN,MAX-1]

val zero15: Bounded[1,5] = 0      // ERROR
val one15: Bounded[1,5] = 1
val two15: Bounded[1,5] = 2

deanwampler

scala> val s = Seq(1.1, "two", 3, BigDecimal(4.4))
val s: Seq[Matchable] = List(1.1, two, 3, 4.4)

scala> s.foldLeft(DTNil)((l,x) => x +: l)
1 |s.foldLeft(DTNil)((l,x) => x +: l)
  |                           ^^^^^^
  |          Found:    DTNonEmptyList[(0 : Int), Matchable, (l : DTNil.type)]
  |          Required: DTNil.type

scala> val seed: DTList[0] = DTNil

deanwampler

scala> val list = 1 +: "two" +: DTNil
val list: DTNonEmptyList[1, Int, ? <: DTNonEmptyList[0, String, DTNil.type]] =
  DTNonEmptyList(1,DTNonEmptyList(two,DTNil))

scala> list.size
     | list.head
     | list.tail
val res0: Int = 2
val res1: Int = 1
val res2: list.T = DTNonEmptyList(two,DTNil)

deanwampler

scala> val zero0: 0 = 0
val zero0: 0 = 0

scala> val zero1: 0 = 1
1 |val zero1: 0 = 1
  |               ^
  |               Found:    (1 : Int)
  |               Required: (0 : Int)

scala> val one0: 1 = 0

deanwampler

// Adapted from
// https://github.com/deanwampler/programming-scala-book-code-examples/blob/master/src/script/scala/progscala3/typesystem/deptypes/DependentTypesSimple.scala

import scala.compiletime.ops.string.* // Scala 2 uses _ as the wild card, which you can still use 

val s1: "ab" + "cd" = "abcd"
val bad2: "ab" + "cd" = "abcdef"  // ERROR

deanwampler

// Adapted from
// https://github.com/deanwampler/programming-scala-book-code-examples/blob/master/src/script/scala/progscala3/typesystem/deptypes/DependentTypesSimple.scala

import scala.compiletime.ops.boolean.* // Scala 2 uses _ as the wild card, which you can still use 

val t1: true = true
val f1: ![true] = false                // Note how the left-hand size has to be written
val tt1: true  && true  = true
val tf1: true  && false = false
val ft1: false && true  = false

deanwampler

// Adapted from
// https://github.com/deanwampler/programming-scala-book-code-examples/blob/master/src/script/scala/progscala3/typesystem/deptypes/DependentTypesSimple.scala

import scala.compiletime.ops.int.S  // In 3.0.0, it's scala.compiletime.S !!

val s1:  S[0] = 1
val s2a: S[S[0]] = 2
val s2b: S[1] = 2      
val s3a: S[S[S[0]]] = 3
val s3b: S[2] = 3

deanwampler

// Adapted from
// https://github.com/deanwampler/programming-scala-book-code-examples/blob/master/src/script/scala/progscala3/typesystem/deptypes/DependentTypesSimple.scala

import scala.compiletime.ops.int.* // Scala 2 uses _ as the wild card, which you can still use 

val i1: 0 + 1     = 0 + 1
val i2: 1 + 1     = 1 + 1
val i3: 1 + 2     = 1 + 2
val i4: 3 * 2 - 1 = 3 * 2 - 1
val i5: 12 / 3    = 4