34 lines
827 B
Rust
34 lines
827 B
Rust
use std::env;
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fn main() {
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match env::vars()
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.map(|(a, _)| a)
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.filter(|x| x.starts_with("CARGO_FEATURE_STM32"))
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.get_one()
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{
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Ok(_) => {}
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Err(GetOneError::None) => panic!("No stm32xx Cargo feature enabled"),
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Err(GetOneError::Multiple) => panic!("Multiple stm32xx Cargo features enabled"),
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}
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}
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enum GetOneError {
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None,
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Multiple,
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}
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trait IteratorExt: Iterator {
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fn get_one(self) -> Result<Self::Item, GetOneError>;
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}
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impl<T: Iterator> IteratorExt for T {
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fn get_one(mut self) -> Result<Self::Item, GetOneError> {
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match self.next() {
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None => Err(GetOneError::None),
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Some(res) => match self.next() {
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Some(_) => Err(GetOneError::Multiple),
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None => Ok(res),
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},
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}
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}
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}
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