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Tweak pattern docs #187

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Mar 11, 2024
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Tweak pattern docs #187

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8766657
Tweak pattern docs
jariji Feb 29, 2024
d4dc465
Update
jariji Feb 29, 2024
80b083a
Remove reference to ADTs
jariji Feb 29, 2024
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27 changes: 15 additions & 12 deletions docs/syntax/pattern.md
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Expand Up @@ -273,26 +273,29 @@ Note that, due to the lack of an operation for distinguishing `nothing` from "ke
Deconstruction of Custom Composite Data
-------------------------------------------

In order to deconstruct arbitrary data types in a similar way to `Tuple`, `Array` and `Dict`, simply declare them to be record types with the `@as_record` macro.

Here is an example, check more about ADTs(and GADTs) at [Algebraic Data Type Syntax in MLStyle](https://thautwarm.github.io/MLStyle.jl/latest/syntax/adt).
Enable pattern matching on the internals of a struct `S` with `@as_record S`.

```julia-console
julia> @data Color begin
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It is not necessary to introduce ADTs here. struct is more familiar and does the job.

RGB(r::Int, g::Int, b::Int)
Gray(Int)
julia> abstract type Color end

julia> struct RGB <: Color
r::Int
g::Int
b::Int
end

julia> # treating those types as records for more flexible pattern matching
julia> struct Gray <: Color
_1::Int
end

julia> @as_record RGB
julia> @as_record RGB;

julia> @as_record Gray
julia> @as_record Gray;

julia> color_to_int(x) = @match x begin
RGB(;r, g, b) => 16 + b + 6g + 36r
Gray(i) => 232 + i
end
RGB(;r, g, b) => 16 + b + 6g + 36r
Gray(i) => 232 + i
end
color_to_int (generic function with 1 method)

julia> RGB(200, 0, 200) |> color_to_int
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