Crate filters

A library for constructing predicates and filters for Iterator::filter

This library offers types and traits for creating filters and combining them with logical operators such as AND, OR, NOT and others.

Example

use filters::filter::Filter;
let a = (|&a: &usize|{ a > 5 }).and_not(|&a: &usize| a < 20).or(|&a: &usize| a == 10);
// We now have ((a > 5) && !(a < 20) ) || a == 10

assert_eq!(a.filter(&21), true);
assert_eq!(a.filter(&10), true);
assert_eq!(a.filter(&11), false);
assert_eq!(a.filter(&5), false);

Ops

Some basic operators are shipped with the library:

• And
• Or
• Not

others are build by combining them. The operators can be used from the filter instance directly, as shown in the example above.

Implementing own filters

One can implement own filters by implementing the Filter trait. Example:

use filters::filter::Filter;
struct EqTo {
    pub i: usize,
}

impl Filter<usize> for EqTo {
    fn filter(&self, n: &usize) -> bool {
        self.i == *n
    }
}

fn filter_with_eqto() {
    let eq = EqTo { i: 0 };
    assert_eq!(eq.filter(&0),  true);
    assert_eq!(eq.filter(&1),  false);
    assert_eq!(eq.filter(&17), false);
    assert_eq!(eq.filter(&42), false);
}

Using in Iterator::filter()

The library is intended to be used in the Iterator::filter() function, but can be used in other places, of course. An example for Iterator::filter():

use filters::filter::Filter;
let v = vec![0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20];
let inrange        = (|&a: &usize| { a > 5 }).and(|&a: &usize| { a < 15 });
let r : Vec<usize> = v.into_iter().filter(|x| inrange.filter(x)).collect();
assert_eq!(r, vec![6, 7, 8, 9, 10, 11, 12, 13, 14]);

Modules

filter	The filter implementation
ops

Macros

impl_operators

Creates operator implementations for a Filter struct Currently only Fn and Filter implementations are handled