Examples

See the languages at work.

These examples are selected from executable fixtures. Dewy and µDewy are related but distinct source languages, so every example is labeled.

Dewy · runs

Hello, World

printl"Hello, World!"

Prelude imports and top-level execution in one line.

Source

Dewy · runs

Array sum

let values:array<int64> = [10 20 12]
let i:int64 = 0
let total:int64 = 0
loop i <? values.length {
    total += values[i]
    i += 1
}

Flow-proven bounds make the indexed access valid.

Source

Dewy · runs

Objects

let point = [
    x = 3
    y = 4
    sum = () => x + y
]
let value = point.sum

Structural fields and methods with object-local lookup.

Source

Dewy · runs

Unicode strings

let text = "café 👨‍👩‍👧‍👦"
let family = text[5]
let count = family.length

Index and length operate on extended grapheme clusters.

Source

Dewy · runs

Stepped ranges

let total:int64 = 0
loop i in 0,2..10 {
    total += i
}
loop i in 5,3..0 {
    total += i
}

A second anchor establishes either a positive or negative step without a separate range constructor.

Source

Dewy · runs

Multiple iterators

let total:int64 = 0
loop i in 0..2 and j in 10..20 {
    total += i
}

Iterator conditions compose directly with logical operators; and stops when either iterator is exhausted.

Source

Dewy · runs

Optional narrowing

let value:int64|none = choose(true)

if value is? int64 {
    return value + 2
}
return 0

A type test narrows the optional value for the successful branch without an assertion or forced unwrap.

Source

Dewy · runs

Overload sets

let choose = (():>int64 => 20)
           & ((x:int64):>int64 => x)

let answer = choose() + choose(22)

& combines ordinary function values, and each call selects the implementation matching its arguments.

Source

Dewy · runs

Defaults and keywords

let add = (x:int64 y:int64=2):>int64 =>
    x + y

let answer = add(40)
let same = add(39 y=3)

Parameters can have lazy defaults, while named arguments make overrides and reordered calls explicit.

Source

Dewy · runs

Modules and paths

from p"lib.dewy" import (answer add Number)
import p"lib.dewy" as library

let value:library.Number = answer
let result = add(value)

Selective and namespaced imports share file-relative path values and one type system across modules.

Source

µDewy · playground

Fibonacci

let fib = (n:int):>int => {
    if n <=? 1 { return n }
    return fib(n - 1) + fib(n - 2)
}

Compile the bootstrap subset entirely in the browser.

Try it

µDewy · runs

Self-hosting

udewy -c \
  udewy/bootstrap/main.udewy

The µDewy compiler is itself implemented in µDewy.

Compiler source

More programs

The repository also contains backend tests, web and SDL demos, games, data structures, graphics experiments, and older design examples. Some files under the top-level examples/ directory describe planned language behavior rather than the current compiler.

Design examples µDewy programs