Array

[uncomputable]

Add array type + expression + example.

[apoelstra]

e38b11393d9ce32fa98cbaa0349d780f24366099 looks good. It's a bit of a surprising restriction that array sizes can only be powers of 2. I wonder if we should change the grammar to require the number be encoded as 2^n rather than n-with-restrictions.

Or are you planning to extend the type to handle arbitrary widths?

Also, is the syntax where you assign numeric literals to e.g. [bool; 128] a special case for boolean arrays?

[uncomputable]

Restricting array sizes to powers of two will confuse people, good point. Right now, arrays are a macro for nested products, but we might want to extend the definition to some sort of balanced binary tree of elements.

Assigning numeric literals to types such as [bool; 128] is in line with one of Simfony's design principles: Macro types behave exactly like the underlying base type. The base type of [bool; 128] and of u128 is the same, so the same values can be assigned to both.

[apoelstra]

The base type of [bool; 128] and of u128 is the same, so the same values can be assigned to both

Sounds good. We should make sure that's clear in the docs.

[uncomputable]

Updated array types to be balanced trees of product types.

If an array has n elements, then we go to the next power of two m ≥ n. We split the array into m / 2 elements and n - m / 2 elements. And so on.

[apoelstra]

ucACK cf49a5cbf8dac8fd2b2cba2e06f475e3626dbce3

At some point soon I should set up a test rig for this repo.

I'd kinda like a unit test for the BTreeSlice type. I think it'd be easy to create a few trees of different sizes with consecutive integers and check that you can fold them down to their sum, for example.

[uncomputable]

Added a test for BTreeSlice::fold.