as_bool 0.1.3

/*! as_bool provides an expanded notion of what is *true* and what is *false*.

    Specifically with the AsBool trait, which an implementing type can
    use to express how it should be represented in a boolean context.

    This crate also provides implementations of AsBool for Rust's builtin types
    and collections from the Standard Library. These implementations provide a
    truth table similar to the *Groovy Truth* implemented in the Groovy
    programming language. The truth table can be described as follow:

    * booleans behave as expected.
    * all non-zero numbers are `true`.
    * `0` , `0.0` , `f32::NAN`, `f64::NAN`, and `'\0'` are `false`.
    * non-empty strings are `true`.
    * empty strings are `false`.
    * non-empty collections are `true`.
    * empty collections are `false`.
    * `None` is always `false`.
    * `Err` is always `false`.
    * `Ok` and `Some` are unwrapped and the contained item is evaluated according
    to the preceding rules.
**/
use std::collections::{BTreeMap, BTreeSet, BinaryHeap, HashMap, HashSet, LinkedList, VecDeque};

/// `AsBool` defines a type's behavior in a boolean context. Basically, it converts
/// the implementing type to `bool`.
pub trait AsBool {
    fn as_bool(&self) -> bool;
}

// Booleans
impl AsBool for bool {
    fn as_bool(&self) -> bool {
        *self
    }
}

// Integers
impl AsBool for usize {
    fn as_bool(&self) -> bool {
        *self != 0
    }
}
impl AsBool for u8 {
    fn as_bool(&self) -> bool {
        *self != 0
    }
}
impl AsBool for u16 {
    fn as_bool(&self) -> bool {
        *self != 0
    }
}
impl AsBool for u32 {
    fn as_bool(&self) -> bool {
        *self != 0
    }
}
impl AsBool for u64 {
    fn as_bool(&self) -> bool {
        *self != 0
    }
}
impl AsBool for u128 {
    fn as_bool(&self) -> bool {
        *self != 0
    }
}
impl AsBool for isize {
    fn as_bool(&self) -> bool {
        *self != 0
    }
}
impl AsBool for i8 {
    fn as_bool(&self) -> bool {
        *self != 0
    }
}
impl AsBool for i16 {
    fn as_bool(&self) -> bool {
        *self != 0
    }
}
impl AsBool for i32 {
    fn as_bool(&self) -> bool {
        *self != 0
    }
}
impl AsBool for i64 {
    fn as_bool(&self) -> bool {
        *self != 0
    }
}
impl AsBool for i128 {
    fn as_bool(&self) -> bool {
        *self != 0
    }
}

// Floats
impl AsBool for f32 {
    fn as_bool(&self) -> bool {
        if self.is_nan() {
            false
        } else {
            *self != 0.0
        }
    }
}
impl AsBool for f64 {
    fn as_bool(&self) -> bool {
        if self.is_nan() {
            false
        } else {
            *self != 0.0
        }
    }
}

// Tuples
impl AsBool for () {
    fn as_bool(&self) -> bool {
        false
    }
}

// Arrays
impl<T> AsBool for [T] {
    fn as_bool(&self) -> bool {
        !self.is_empty()
    }
}

// Collections
impl<T> AsBool for Vec<T> {
    fn as_bool(&self) -> bool {
        !self.is_empty()
    }
}
impl<T> AsBool for VecDeque<T> {
    fn as_bool(&self) -> bool {
        !self.is_empty()
    }
}
impl<T> AsBool for LinkedList<T> {
    fn as_bool(&self) -> bool {
        !self.is_empty()
    }
}
impl<K, V> AsBool for HashMap<K, V> {
    fn as_bool(&self) -> bool {
        !self.is_empty()
    }
}
impl<K, V> AsBool for BTreeMap<K, V> {
    fn as_bool(&self) -> bool {
        !self.is_empty()
    }
}
impl<T, S> AsBool for HashSet<T, S> {
    fn as_bool(&self) -> bool {
        !self.is_empty()
    }
}
impl<T> AsBool for BTreeSet<T> {
    fn as_bool(&self) -> bool {
        !self.is_empty()
    }
}
impl<T> AsBool for BinaryHeap<T> {
    fn as_bool(&self) -> bool {
        !self.is_empty()
    }
}

// Text
impl AsBool for char {
    fn as_bool(&self) -> bool {
        *self != '\0'
    }
}
impl AsBool for &str {
    fn as_bool(&self) -> bool {
        !self.is_empty()
    }
}
impl AsBool for String {
    fn as_bool(&self) -> bool {
        !self.is_empty()
    }
}

// Option
impl<T: AsBool> AsBool for Option<T> {
    fn as_bool(&self) -> bool {
        if let Some(t) = self {
            t.as_bool()
        } else {
            false
        }
    }
}

// Result
impl<T: AsBool, E> AsBool for std::result::Result<T, E> {
    fn as_bool(&self) -> bool {
        if let Ok(t) = self {
            t.as_bool()
        } else {
            false
        }
    }
}

// Tests
#[cfg(test)]
mod tests {
    use crate::AsBool;
    use std::collections::{
        BTreeMap, BTreeSet, BinaryHeap, HashMap, HashSet, LinkedList, VecDeque,
    };

    #[test]
    fn the_works() {
        assert!(true.as_bool());
        assert!(!false.as_bool());
        assert!((1 as usize).as_bool());
        assert!(!(0 as usize).as_bool());
        assert!((1 as u8).as_bool());
        assert!(!(0 as u8).as_bool());
        assert!((1 as u16).as_bool());
        assert!(!(0 as u16).as_bool());
        assert!((1 as u32).as_bool());
        assert!(!(0 as u32).as_bool());
        assert!((1 as u64).as_bool());
        assert!(!(0 as u64).as_bool());
        assert!((1 as u128).as_bool());
        assert!(!(0 as u128).as_bool());
        assert!((1 as isize).as_bool());
        assert!(!(0 as isize).as_bool());
        assert!((1 as i8).as_bool());
        assert!(!(0 as i8).as_bool());
        assert!((1 as i16).as_bool());
        assert!(!(0 as i16).as_bool());
        assert!((1 as i32).as_bool());
        assert!(!(0 as i32).as_bool());
        assert!((1 as i64).as_bool());
        assert!(!(0 as i64).as_bool());
        assert!((1 as i128).as_bool());
        assert!(!(0 as i128).as_bool());
        assert!((1.0 as f32).as_bool());
        assert!(!(0.0 as f32).as_bool());
        assert!((1.0 as f64).as_bool());
        assert!(!(0.0 as f64).as_bool());
        assert!(!(f32::NAN).as_bool());
        assert!(!(f64::NAN).as_bool());
        assert!('a'.as_bool());
        assert!(!'\0'.as_bool());
        assert!("a".as_bool());
        assert!(!"".as_bool());
        assert!("a".to_string().as_bool());
        assert!(!"".to_string().as_bool());

        assert!(!().as_bool());
        assert!(![true; 0].as_bool());
        assert!([true; 1].as_bool());

        let mut hm: HashMap<u8, bool> = HashMap::new();
        assert!(!hm.as_bool());
        hm.insert(1, true);
        assert!(hm.as_bool());

        let mut bm: BTreeMap<u8, bool> = BTreeMap::new();
        assert!(!bm.as_bool());
        bm.insert(1, true);
        assert!(bm.as_bool());

        let mut hs: HashSet<bool> = HashSet::new();
        assert!(!hs.as_bool());
        hs.insert(true);
        assert!(hs.as_bool());

        let mut bs: BTreeSet<bool> = BTreeSet::new();
        assert!(!bs.as_bool());
        bs.insert(true);
        assert!(bs.as_bool());

        let mut bh: BinaryHeap<bool> = BinaryHeap::new();
        assert!(!bh.as_bool());
        bh.push(true);
        assert!(bh.as_bool());

        let mut l: LinkedList<bool> = LinkedList::new();
        assert!(!l.as_bool());
        l.push_back(true);
        assert!(l.as_bool());

        let mut vd: VecDeque<bool> = VecDeque::new();
        assert!(!vd.as_bool());
        vd.push_back(true);
        assert!(vd.as_bool());

        let mut v: Vec<bool> = Vec::new();
        assert!(!v.as_bool());
        v.push(true);
        assert!(v.as_bool());

        assert!(Some(true).as_bool());
        assert!(!Some(false).as_bool());
        let n: Option<bool> = None;
        assert!(!n.as_bool());
        let mut o: Result<bool, bool> = Ok(true);
        let mut e: Result<bool, bool> = Err(true);
        assert!(o.as_bool());
        assert!(!e.as_bool());
        o = Ok(false);
        e = Err(false);
        assert!(!o.as_bool());
        assert!(!e.as_bool());
    }
}