Experimentation with extensibility, such as it is

implementations/rust/examples/Makefile

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+BINARY_FILES=known-data.bin unknown-data.bin
+
+all: $(BINARY_FILES)
+
+%.bin: %.txt Makefile
+	racket ../../racket/preserves/preserves/tool.rkt --atob --no-annotations < $< > $@.tmp || (rm -f $@.tmp; false)
+	mv $@.tmp $@
+
+clean:
+	rm -f $(BINARY_FILES)

implementations/rust/examples/extensibility.rs

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+use preserves::{de, value, value::decoder};
+use serde::{Serialize, Deserialize};
+use std::fs::File;
+use std::io::Error;
+
+#[derive(Debug, Serialize, Deserialize, PartialEq)]
+enum Fruit {
+    Apple(Colour),
+    Pear(Variety),
+    Banana(Weight, Colour, u8),
+
+    // Peach,
+
+    #[serde(other)]
+    Unknown,
+}
+
+#[derive(Debug, Serialize, Deserialize, PartialEq)]
+#[serde(rename = "kilograms")]
+struct Weight(f32);
+
+#[derive(Debug, Serialize, Deserialize, PartialEq)]
+struct Colour {
+    name: String,
+}
+
+#[derive(Debug, Serialize, Deserialize, PartialEq)]
+enum Variety {
+    Conference,
+    Bosc,
+    European,
+    Anjou,
+}
+
+fn try_file(kind: &str, path: &str) -> Result<(), Error> {
+    let fruits_value = decoder::from_read(&mut File::open(path)?).demand_next()?;
+    println!("{:?}", fruits_value);
+
+    let fruits1: Vec<Fruit> = value::de::from_value(&fruits_value)?;
+    println!("(via generic decoding) {}: {:?}", kind, fruits1);
+
+    let fruits2: Vec<Fruit> = de::from_read(&mut File::open(path)?)?;
+    println!("(direct from binary)   {}: {:?}\n", kind, fruits2);
+
+    assert_eq!(fruits1, fruits2);
+    Ok(())
+}
+
+fn main() -> Result<(), Error> {
+    try_file("KNOWN", "examples/known-data.bin")?;
+    try_file("UNKNOWN", "examples/unknown-data.bin")?;
+    Ok(())
+}

implementations/rust/examples/known-data.bin

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+”‚uApple‚vColourSred‚uApple‚vColourUgreen„vBanana‚ykilograms?¾¸Që…¸‚vColourXbrownish5‚tPear<61>zConference

implementations/rust/examples/known-data.txt

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+@<EmacsMode "-*- preserves -*-">
+[
+  <Apple <Colour "red">>
+  <Apple <Colour "green">>
+  <Banana <kilograms 0.12> <Colour "brownish"> 5>
+  <Pear <Conference>>
+]

implementations/rust/examples/unknown-data.bin

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+浮uAppleＷColourSred「PeachＶAppleＷColourUgreen<EFBFBD>BananaＺkilograms?ｾｸQ<EFBDB8>ｸＷColourXbrownish5ｲxripeness『SquishyＵPear】Conference

implementations/rust/examples/unknown-data.txt

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+@<EmacsMode "-*- preserves -*-">
+[
+  <Apple <Colour "red">>
+  <Peach>
+  <Apple <Colour "green">>
+  <Banana <kilograms 0.12> <Colour "brownish"> 5 {ripeness: <Squishy>}>
+  <Pear <Conference>>
+]