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March 21, 2019 12:25
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#![allow(non_snake_case)] | |
#![feature(test)] | |
extern crate test; | |
use std::iter::FromIterator; | |
#[cfg(test)] | |
use test::Bencher; | |
#[derive(Copy, Clone, PartialEq, Eq, Debug)] | |
struct LastOne<T>(Option<T>); | |
impl<T> FromIterator<T> for LastOne<T> { | |
#[inline] | |
fn from_iter<I: IntoIterator<Item = T>>(iter: I) -> LastOne<T> { | |
LastOne(iter.into_iter().last()) | |
} | |
} | |
type Last<T> = LastOne<T>; | |
impl<T> Last<T> { | |
fn new(x: T) -> Last<T> { LastOne(Some(x)) } | |
} | |
fn from_iter_baseline<C, T, E, I>(iter: I) -> Result<C, E> | |
where I: Iterator<Item = Result<T, E>>, | |
C: FromIterator<T>, | |
{ | |
FromIterator::from_iter(iter) | |
} | |
fn from_iter_adapter<C, T, E, I>(iter: I) -> Result<C, E> | |
where I: Iterator<Item = Result<T, E>>, | |
C: FromIterator<T>, | |
{ | |
struct Adapter<Iter, E> { | |
iter: Iter, | |
err: Option<E>, | |
} | |
impl<T, E, Iter: Iterator<Item=Result<T, E>>> Iterator for Adapter<Iter, E> { | |
type Item = T; | |
#[inline] | |
fn next(&mut self) -> Option<T> { | |
match self.iter.next() { | |
Some(Ok(value)) => Some(value), | |
Some(Err(err)) => { | |
self.err = Some(err); | |
None | |
} | |
None => None, | |
} | |
} | |
fn size_hint(&self) -> (usize, Option<usize>) { | |
let (_min, max) = self.iter.size_hint(); | |
(0, max) | |
} | |
} | |
let mut adapter = Adapter { iter: iter, err: None }; | |
let v: C = FromIterator::from_iter(adapter.by_ref()); | |
match adapter.err { | |
Some(err) => Err(err), | |
None => Ok(v), | |
} | |
} | |
fn from_iter_with_scan_with_freevar<C, T, E, I>(iter: I) -> Result<C, E> | |
where I: Iterator<Item = Result<T, E>>, | |
C: FromIterator<T>, | |
{ | |
let mut err = None; | |
let v = { | |
let adapter = iter.scan((), |_, item| { | |
match item { | |
Ok(x) => Some(x), | |
Err(x) => { | |
err = Some(x); | |
None | |
}, | |
} | |
}); | |
FromIterator::from_iter(adapter) | |
}; | |
match err { | |
Some(err) => Err(err), | |
None => Ok(v), | |
} | |
} | |
fn from_iter_with_scan_passing_state<C, T, E, I>(iter: I) -> Result<C, E> | |
where I: Iterator<Item = Result<T, E>>, | |
C: FromIterator<T>, | |
{ | |
let mut err = None; | |
let v = { | |
let adapter = iter.scan(&mut err, |err, item| { | |
match item { | |
Ok(x) => Some(x), | |
Err(x) => { | |
**err = Some(x); | |
None | |
}, | |
} | |
}); | |
FromIterator::from_iter(adapter) | |
}; | |
match err { | |
Some(err) => Err(err), | |
None => Ok(v), | |
} | |
} | |
fn from_iter_with_filter_map<C, T, E, I>(iter: I) -> Result<C, E> | |
where I: Iterator<Item = Result<T, E>>, | |
C: FromIterator<T>, | |
{ | |
let mut err = None; | |
let v = { | |
let adapter = iter.filter_map(|item| { | |
match item { | |
Ok(x) => Some(x), | |
Err(x) => { | |
err = Some(x); | |
None | |
}, | |
} | |
}); | |
FromIterator::from_iter(adapter) | |
}; | |
match err { | |
Some(err) => Err(err), | |
None => Ok(v), | |
} | |
} | |
fn main() { | |
let one_a: Result<Last<u8>, _> = from_iter_baseline("1,2,3".split(",").map(|x| x.parse())); | |
let one_b: Result<Last<u8>, _> = from_iter_adapter("1,2,3".split(",").map(|x| x.parse())); | |
let two_a: Result<Last<u8>, _> = from_iter_with_scan_passing_state("1,2,3".split(",").map(|x| x.parse())); | |
let two_b: Result<Last<u8>, _> = from_iter_with_scan_with_freevar("1,2,3".split(",").map(|x| x.parse())); | |
let three: Result<Last<u8>, _> = from_iter_with_filter_map("1,2,3".split(",").map(|x| x.parse())); | |
println!("{:?}", one_a); | |
println!("{:?}", one_b); | |
println!("{:?}", two_a); | |
println!("{:?}", two_b); | |
println!("{:?}", three); | |
let one_a: Result<Last<u8>, _> = from_iter_baseline("1,a,3".split(",").map(|x| x.parse())); | |
let one_b: Result<Last<u8>, _> = from_iter_adapter("1,a,3".split(",").map(|x| x.parse())); | |
let two_a: Result<Last<u8>, _> = from_iter_with_scan_passing_state("1,a,3".split(",").map(|x| x.parse())); | |
let two_b: Result<Last<u8>, _> = from_iter_with_scan_with_freevar("1,a,3".split(",").map(|x| x.parse())); | |
let three: Result<Last<u8>, _> = from_iter_with_filter_map("1,a,3".split(",").map(|x| x.parse())); | |
println!("{:?}", one_a); | |
println!("{:?}", one_b); | |
println!("{:?}", two_a); | |
println!("{:?}", two_b); | |
println!("{:?}", three); | |
} | |
#[bench] | |
fn bench__vec_from_iter_using_baseline___(b: &mut Bencher) { | |
let expected = vec![1; 1000]; | |
let v: Vec<Result<isize, String>> = vec![Ok(1); 1000]; | |
b.iter(|| { | |
let result: Result<Vec<isize>, String> = from_iter_baseline(v.iter().cloned()); | |
assert_eq!(result.unwrap(), expected); | |
}); | |
} | |
#[bench] | |
fn bench__vec_from_iter_using_adapter____(b: &mut Bencher) { | |
let expected = vec![1; 1000]; | |
let v: Vec<Result<isize, String>> = vec![Ok(1); 1000]; | |
b.iter(|| { | |
let result: Result<Vec<isize>, String> = from_iter_adapter(v.iter().cloned()); | |
assert_eq!(result.unwrap(), expected); | |
}); | |
} | |
#[bench] | |
fn bench__vec_from_iter_with_scan_param__(b: &mut Bencher) { | |
let expected = vec![1; 1000]; | |
let v: Vec<Result<isize, String>> = vec![Ok(1); 1000]; | |
b.iter(|| { | |
let result: Result<Vec<isize>, String> = from_iter_with_scan_passing_state(v.iter().cloned()); | |
assert_eq!(result.unwrap(), expected); | |
}); | |
} | |
#[bench] | |
fn bench__vec_from_iter_with_scan_freevar(b: &mut Bencher) { | |
let expected = vec![1; 1000]; | |
let v: Vec<Result<isize, String>> = vec![Ok(1); 1000]; | |
b.iter(|| { | |
let result: Result<Vec<isize>, String> = from_iter_with_scan_with_freevar(v.iter().cloned()); | |
assert_eq!(result.unwrap(), expected); | |
}); | |
} | |
#[bench] | |
fn bench__vec_from_iter_with_filter_map__(b: &mut Bencher) { | |
let expected = vec![1; 1000]; | |
let v: Vec<Result<isize, String>> = vec![Ok(1); 1000]; | |
b.iter(|| { | |
let result: Result<Vec<isize>, String> = from_iter_with_filter_map(v.iter().cloned()); | |
assert_eq!(result.unwrap(), expected); | |
}); | |
} | |
#[bench] | |
fn bench_last_from_iter_using_baseline___(b: &mut Bencher) { | |
let expected = Last::new(1); | |
let v: Vec<Result<isize, String>> = vec![Ok(1); 3000]; | |
b.iter(|| { | |
let result: Result<Last<isize>, String> = from_iter_baseline(v.iter().cloned()); | |
assert_eq!(result.unwrap(), expected); | |
}); | |
} | |
#[bench] | |
fn bench_last_from_iter_using_adapter____(b: &mut Bencher) { | |
let expected = Last::new(1); | |
let v: Vec<Result<isize, String>> = vec![Ok(1); 3000]; | |
b.iter(|| { | |
let result: Result<Last<isize>, String> = from_iter_adapter(v.iter().cloned()); | |
assert_eq!(result.unwrap(), expected); | |
}); | |
} | |
#[bench] | |
fn bench_last_from_iter_with_scan_param__(b: &mut Bencher) { | |
let expected = Last::new(1); | |
let v: Vec<Result<isize, String>> = vec![Ok(1); 3000]; | |
b.iter(|| { | |
let result: Result<Last<isize>, String> = from_iter_with_scan_passing_state(v.iter().cloned()); | |
assert_eq!(result.unwrap(), expected); | |
}); | |
} | |
#[bench] | |
fn bench_last_from_iter_with_scan_freevar(b: &mut Bencher) { | |
let expected = Last::new(1); | |
let v: Vec<Result<isize, String>> = vec![Ok(1); 3000]; | |
b.iter(|| { | |
let result: Result<Last<isize>, String> = from_iter_with_scan_with_freevar(v.iter().cloned()); | |
assert_eq!(result.unwrap(), expected); | |
}); | |
} | |
#[bench] | |
fn bench_last_from_iter_with_filter_map__(b: &mut Bencher) { | |
let expected = Last::new(1); | |
let v: Vec<Result<isize, String>> = vec![Ok(1); 3000]; | |
b.iter(|| { | |
let result: Result<Last<isize>, String> = from_iter_with_filter_map(v.iter().cloned()); | |
assert_eq!(result.unwrap(), expected); | |
}); | |
} |
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