titlefmt 0.4.0

Metadata Title Formatting Library
Documentation 
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use super::Error;
use expression::{Evaluation, Expression, Value};
use metadata;

/// XOR operation
/// test if an odd number of arguments evaluate to true
/// to achieve that: filter out the false expressions and count the remaining (true) expressions
pub fn xor<T: metadata::Provider>(
    expressions: &[Box<Expression<T>>],
    provider: &T,
) -> Result<Evaluation, Error> {
    let result: usize = expressions
        .iter()
        .filter(|&expr| expr.apply(provider).truth())
        .count();
    let is_odd: bool = result % 2 == 1;
    Ok(Evaluation::new(Value::Empty, is_odd))
}

#[cfg(test)]
mod test;