Wasmer Pack
Tutorials
Variants

Variants

Intro

  • A promise statement
    • We're going to introduce variants
    • Similar to Rust's enum or TypeScript's tagged union
  • A preview of what's to come

Body

Brief recap of how sum types work, drawing parallels to similar constructs in existing languages.

Point out two special variants, option<T> and expected<T, E>

  • Draw parallels with Rust
  • Show examples of what wai-bindgen generates for Python and JavaScript

Define the WIT file:

// calculator.wai
 
variant instruction {
    add(i32),
    subtract(i32),
    multiply(i32),
    divide(i32),
}
 
record out-of-bounds-error {
    value: i32,
    min: i32,
    max: i32,
}
 
variant error {
    divide-by-zero,
    out-of-bounds(out-of-bounds-error),
}
 
/// Execute a sequence of instructions on a number.
///
/// This is a basic calculator!
calculate: func(start: i32, instructions: list<intruction>) -> expected<i32, error>

Implement the guest:

  • Handle divide by zero
  • Hard-code a limit of (-10, 50) for the value
  • Publish to WAPM (links, etc.)

Use the bindings:

  • Create a Python project
  • Create a JavaScript project
    • Show how you handle errors in TypeScript (switch-case, etc.)

Conclusion

  • Reminder of how helpful the guide is
  • Reiterate how important your topic is
  • Call-to-action
    • Add different error cases
    • Develop your own abstractions for working with errors

Checklist

Inspiration 💡

  • Read articles and watch videos that inspire me
  • Brainstorm the topics that I want to write about in bullet points
  • Reorder those bullet points to create a line of thought

Draft ✏

  • Expand those bullet points into sentences/text
  • Go over the document

Ready to Publish 🗞

  • Draft 5 titles and pick one
  • Revise the complete text for typos
  • Preview the text
  • Publish or schedule the post
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