Gengoscript Tutorial: First Script¶

This walkthrough takes you from a fresh build to a small working script.

If you only need the command summary, see quickstart.md.

This walkthrough assumes wasmtime is installed and available on PATH.

1. Build the WASI Runtime¶

zig build -Dpreset=dev wasi

2. Create a Script¶

Create examples/hello_tutorial.gengo:

std := import("std")

name := "gengo"
nums := [2, 3, 4]

std.io.println("hello", name)
std.io.println(std.core.len("åäö"))
std.io.println(std.core.bytelen("åäö"))
std.io.println(std.conv.to_string(`🙂`))
std.io.println(nums[1])

3. Run It¶

wasmtime --dir . ./build/gengo-runtime.wasm -- examples/hello_tutorial.gengo

Expected output:

hello gengo
3
6
🙂
3

4. Add a Type Contract¶

Replace the file contents with:

std := import("std")

type User struct { name string, initial rune }

func greet(u User) {
  std.io.println(u.name, std.conv.to_string(u.initial))
}

greet(User{ name: "Ada", initial: `A` })

Run it again:

wasmtime --dir . ./build/gengo-runtime.wasm -- examples/hello_tutorial.gengo

Expected output:

Ada A

The important point is that the type contract lives inside the script. Invalid values fail where they are constructed, not later in host-side validation code.

5. Check the Environment¶

Run the conformance suite:

zig build -Dpreset=dev test

Run parity checks:

zig build -Dpreset=dev parity

If you are working on runtime behaviour, also run:

zig build -Dpreset=stress test