Crate iter_group

Extends iterators for grouping their values into a mapping type whose values are a collection.

Example 1

use std::collections::{BTreeMap, HashMap};
use iter_group::IntoGroup;

let v = vec![(1, 'a'), (2, 'b'), (3, 'c'), (2, 'd'), (1, 'e'), (1, 'f')];

let h = v.iter().cloned().group::<HashMap<_, Vec<_>>>();
assert_eq!(h.get(&1), Some(&vec!['a', 'e', 'f']));
assert_eq!(h.get(&2), Some(&vec!['b', 'd']));
assert_eq!(h.get(&3), Some(&vec!['c']));

let b = v.iter().cloned().group::<BTreeMap<_, Vec<_>>>();
assert_eq!(b.get(&1), Some(&vec!['a', 'e', 'f']));
assert_eq!(b.get(&2), Some(&vec!['b', 'd']));
assert_eq!(b.get(&3), Some(&vec!['c']));

Example 2

use std::collections::{BTreeMap, HashMap};
use iter_group::IntoGroup;

let v = vec![Some((1, 'a')), Some((2, 'b')), Some((1, 'c'))];

let h = v.iter().cloned().group::<Option<HashMap<_, Vec<_>>>>().unwrap();
assert_eq!(h.get(&1), Some(&vec!['a', 'c']));
assert_eq!(h.get(&2), Some(&vec!['b']));

let b = v.iter().cloned().group::<Option<BTreeMap<_, Vec<_>>>>().unwrap();
assert_eq!(b.get(&1), Some(&vec!['a', 'c']));
assert_eq!(b.get(&2), Some(&vec!['b']));

let v = vec![Some((1, 'a')), None, Some((2, 'b'))];
assert!(v.iter().cloned().group::<Option<HashMap<_, Vec<_>>>>().is_none());
assert!(v.iter().cloned().group::<Option<BTreeMap<_, Vec<_>>>>().is_none());

Example 3

use std::collections::{BTreeMap, HashMap};
use iter_group::IntoGroup;

let v = vec![Ok((1, 'a')), Ok((2, 'b')), Ok((1, 'c'))];

let h = v.iter().cloned().group::<Result<HashMap<_, Vec<_>>, ()>>().unwrap();
assert_eq!(h.get(&1), Some(&vec!['a', 'c']));
assert_eq!(h.get(&2), Some(&vec!['b']));

let b = v.iter().cloned().group::<Result<BTreeMap<_, Vec<_>>, ()>>().unwrap();
assert_eq!(b.get(&1), Some(&vec!['a', 'c']));
assert_eq!(b.get(&2), Some(&vec!['b']));

let v = vec![Ok((1, 'a')), Err(()), Ok((2, 'b'))];
assert!(v.iter().cloned().group::<Result<HashMap<_, Vec<_>>, ()>>().is_err());
assert!(v.iter().cloned().group::<Result<BTreeMap<_, Vec<_>>, ()>>().is_err());

Also offers the option to extend iterators for summarizing their values into a mapping type whose values are a sum.

Example 1

use std::collections::{BTreeMap, HashMap};
use iter_group::IntoSummary;

let v = vec![('a', 1), ('b', 1), ('a', 2), ('b', 2), ('a', 3)];

let h = v.iter().cloned().summarize::<HashMap<_, _>>();
assert_eq!(h.get(&'a'), Some(&6));
assert_eq!(h.get(&'b'), Some(&3));

let b = v.iter().cloned().summarize::<BTreeMap<_, _>>();
assert_eq!(b.get(&'a'), Some(&6));
assert_eq!(b.get(&'b'), Some(&3));

Example 2

use std::collections::{BTreeMap, HashMap};
use iter_group::IntoSummary;

let v = vec![Some(('a', 1)), Some(('b', 2)), Some(('a', 3))];

let h = v.iter().cloned().summarize::<Option<HashMap<_, _>>>().unwrap();
assert_eq!(h.get(&'a'), Some(&4));
assert_eq!(h.get(&'b'), Some(&2));

let b = v.iter().cloned().summarize::<Option<BTreeMap<_, _>>>().unwrap();
assert_eq!(b.get(&'a'), Some(&4));
assert_eq!(b.get(&'b'), Some(&2));

let v = vec![Some(('a', 1)), None, Some(('b', 2))];
assert!(v.iter().cloned().summarize::<Option<HashMap<_, _>>>().is_none());
assert!(v.iter().cloned().summarize::<Option<BTreeMap<_, _>>>().is_none());

Example 3

use std::collections::{BTreeMap, HashMap};
use iter_group::IntoSummary;

let v = vec![Ok(('a', 1)), Ok(('b', 2)), Ok(('a', 3))];

let h = v.iter().cloned().summarize::<Result<HashMap<_, _>, ()>>().unwrap();
assert_eq!(h.get(&'a'), Some(&4));
assert_eq!(h.get(&'b'), Some(&2));

let b = v.iter().cloned().summarize::<Result<BTreeMap<_, _>, ()>>().unwrap();
assert_eq!(b.get(&'a'), Some(&4));
assert_eq!(b.get(&'b'), Some(&2));

let v = vec![Ok(('a', 1)), Err(()), Ok(('b', 2))];
assert!(v.iter().cloned().summarize::<Result<HashMap<_, _>, ()>>().is_err());
assert!(v.iter().cloned().summarize::<Result<BTreeMap<_, _>, ()>>().is_err());

Traits

GroupFromIterator

Implemented by mapping types (HashMap and BTreeMap) such that they can populated by an iterator. Roughly analogous to the FromIterator trait.

InsertAndExtend

A trait for mapping types to serve as a trivial wrapper over the Entry interface.

InsertAndIncrement

A trait for mapping types to serve as a trivial wrapper over the Entry interface

IntoGroup

Extends Iterators with an additional grouping method.

IntoSummary

Extends Iterators with an additional grouping method.

SummarizeFromIterator

Implemented by mapping types (HashMap and BTreeMap) such that they can populated by an iterator. Roughly analogous to the FromIterator trait.