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    // Copyright 2015-2017 Parity Technologies (UK) Ltd.
    // This file is part of Parity.

    // Parity is free software: you can redistribute it and/or modify
    // it under the terms of the GNU General Public License as published by
    // the Free Software Foundation, either version 3 of the License, or
    // (at your option) any later version.

    // Parity is distributed in the hope that it will be useful,
    // but WITHOUT ANY WARRANTY; without even the implied warranty of
    // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    // GNU General Public License for more details.

    // You should have received a copy of the GNU General Public License
    // along with Parity.  If not, see <http://www.gnu.org/licenses/>.

    //! Vector extensions.

    /// Returns len of prefix shared with elem
    ///
    /// ```rust
    ///	extern crate ethcore_util as util;
    ///	use util::vector::SharedPrefix;
    ///
    ///	fn main () {
    ///		let a = vec![1,2,3,3,5];
    ///		let b = vec![1,2,3];
    ///		assert_eq!(a.shared_prefix_len(&b), 3);
    ///	}
    /// ```
    pub trait SharedPrefix<T> {
    	/// Get common prefix length
    	fn shared_prefix_len(&self, elem: &[T]) -> usize;
    }

    impl<T> SharedPrefix<T> for [T] where T: Eq {
    	fn shared_prefix_len(&self, elem: &[T]) -> usize {
    		use std::cmp;
    		let len = cmp::min(self.len(), elem.len());
    		(0..len).take_while(|&i| self[i] == elem[i]).count()
    	}
    }

    #[cfg(test)]
    mod test {
    	use vector::SharedPrefix;

    	#[test]
    	fn test_shared_prefix() {
    		let a = vec![1,2,3,4,5,6];
    		let b = vec![4,2,3,4,5,6];
    		assert_eq!(a.shared_prefix_len(&b), 0);
    	}

    	#[test]
    	fn test_shared_prefix2() {
    		let a = vec![1,2,3,3,5];
    		let b = vec![1,2,3];
    		assert_eq!(a.shared_prefix_len(&b), 3);
    	}

    	#[test]
    	fn test_shared_prefix3() {
    		let a = vec![1,2,3,4,5,6];
    		let b = vec![1,2,3,4,5,6];
    		assert_eq!(a.shared_prefix_len(&b), 6);
    	}
    }

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