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
- Show how you might handle errors using isinstance()
- Show the version with Python's Structural Pattern Matching (opens in a new tab)
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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