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Comment by floitsch | Hacker News Reader

For those interested in a comparison to MicroPython: I recently wrote a Toit version of the MakePython ESP32 Dev Kit lessons.

Here is the Toit version of it: https://docs.google.com/document/d/1K-TYea7jbYfj2ecMUmr0T0zd...

And here the MicroPython: https://www.makerfabs.com/desfile/files/Get-Started-MicroPyt...

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Thanks for sharing. Complex examples like these are great to highlight syntax which simpler examples never mention. For example (heart rate sensor excerpt):

    remembered_ = List width/2: initial_value
    half_height := height / 2
    ...
    min_value := remembered_.reduce: | a b | min a b

These lines (with seemingly context-sensitive meanings for the / and : characters) feel less obvious to me than the examples on the home page.

The `:` are actually doing the same thing, introducing a block (think of it like a limited function).

The `/` are also the same (division), but it's true that we also use `/` to introduce types. For example `x/int`.

I think Toit is relatively easy to learn, but there are definitely a few things that need explaining in the beginning.

Excuse my idle curiosity, but... slash for type ascription? How did that happen? The only precedent I can think of is Prolog’s arity annotations (and jq’s, but I suspect a direct influence there). Does this come from some chunk of programming-language lore I’m unaware of?

It’s also used in Elixir and Erlang for arity, but now that I think about it, it’s probably descended directly from Prolog.

We couldn't use `:` as that one is already used for too many things.

We then experimented with different tokens, and `/` felt best.

Wadler’s law or not, I’m not criticising, just curious :) Thank you (and 'EricCorry in sibling comment) for taking the time to answer!

[Yes, colons are nice as block introducers but don’t play nice with colons for type ascription, which is where we got Python’s asinine f(x: int, y: bool) -> str; don’t know why Rust went with that instead of ML’s uniform f(x: int, y bool): str.]

Answers from the implementors, awesome!

Part of it is that we already used colon for several things.

Also types are optional in Toit, so they are a bit like comments (though they are now checked so they are less like comments now). So they look a little like // comments.

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