69 lines
1.6 KiB
Rust
69 lines
1.6 KiB
Rust
use enve::{
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estring::{self, Aggregatable, Aggregate},
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Product, SepVec, Sum,
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};
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type PlusVec<T> = SepVec<T, '+'>;
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type MulVec<T> = SepVec<T, '*'>;
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const HELP_MESSAGE: &str = "
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USAGE:
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E=10+10*2-4 cargo run --example calc --all-features
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";
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fn main() -> Result<(), enve::Error> {
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let res: f32 = enve::get::<Sum<PlusVec<MinusVec<Product<MulVec<f32>>>>>>("E")
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.map_err(|err| {
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match err {
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enve::Error::NotPresent => eprintln!("The expression was not found"),
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rest => eprintln!("ERROR: {}", rest),
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}
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eprintln!("{}", HELP_MESSAGE);
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std::process::exit(0);
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})
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.unwrap()
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.agg();
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println!("result: {}", res);
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Ok(())
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}
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struct MinusVec<T>(Vec<T>);
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impl<T> estring::ParseFragment for MinusVec<T>
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where
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T: estring::ParseFragment,
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{
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fn parse_frag(es: estring::EString) -> estring::Result<Self> {
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let mut prev: Option<&str> = None;
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es.split('-')
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.map(str::trim)
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.map(|val| match prev.replace(val) {
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None => String::from(val),
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Some(_) => {
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let mut s = val.to_owned();
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s.insert(0, '-');
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s
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}
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})
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.filter(|val| !val.is_empty())
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.map(estring::EString::from)
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.map(T::parse_frag)
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.collect::<estring::Result<Vec<T>>>()
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.map(Self)
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}
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}
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impl<T> estring::Aggregatable for MinusVec<T>
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where
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T: Aggregatable,
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{
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type Item = T::Item;
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fn items(self) -> Vec<Self::Item> {
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self.0.into_iter().flat_map(T::items).collect()
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}
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}
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