The Big Table

After walking through the individual type chapters, it’s useful to have one compact place where the main constructions and destructions sit side by side.

This chapter is a cheat sheet, not a replacement for the explanations in the earlier chapters. The first table summarizes the expression syntax you’ve already seen.

The second table does the same from the point of view of process syntax. If you haven’t read the next section on process syntax yet, feel free to skip that table for now and come back to it later.

Expression syntax

Type Construction Destruction 
type Unit = !

let value = !

let ! = value

type Either = either {
  .left String,
  .right Int,
}

let value: Either = .left "Hello!"

let result = value.case {
  .left str => String.Length(str),
  .right num => Int.Mul(num, 5),
}

type Pair = (String) Int

let value = ("Hello!") 42

let (str) num = value

type Function = [Int] String

let value = [num: Int] Int.ToString(num)

let str = value(42)

type Choice = choice {
  .left => String,
  .right => Int,
}

let value: Choice = case {
  .left => "Hello!",
  .right => 42,
}

let num = value.right

type Continuation = ?
No expression syntax No expression syntax

Process syntax

Type Construction Destruction 
type Unit = !

let value = chan c {
  c!
}

value?

type Either = either {
  .left String,
  .right Int,
}

let value: Either = chan c {
  c.left
  c <> "Hello!"
}

value.case {
  .left => {
    let result = String.Length(value)
  }
  .right => {
    let result = Int.Mul(value, 5)
  }
}
// `result` is in scope here

type Pair = (String) Int

let value = chan c {
  c("Hello!")
  c <> 42
}

value[str]
let num = value

type Function = [Int] String

let value = chan c {
  c[num: Int]
  c <> Int.ToString(num)
}

value(42)
let result = value

type Choice = choice {
  .left => String,
  .right => Int,
}

let value = chan c {
  c.case {
    .left  => { c <> "Hello!" }
    .right => { c <> 42 }
  }
}

value.right
let num = value

type Continuation = ?

let outer: ! = chan break {
  let value: ? = chan c {
    c?     // construction
    break!
  }
  value!   // destruction
}
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