66 lines
1.7 KiB
Rust
66 lines
1.7 KiB
Rust
use crate::Token;
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/// Given two lists of tokens, returns the offset in the first (old) list from which the two lists have the same tokens until the end of the first list.
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/// Thus, the suffix of the old list from the offset to the end is equal to a prefix of the new list.
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///
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/// If there is no overlap, the function returns the maxmium offset, the length of the old list.
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///
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/// ## Example
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/// ```
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/// old: [0, 1, 9, 0, 2, 5]
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/// new: [9, 0, 2, 5, 1]
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/// ```
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/// > results in an offset of 2
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pub fn find_common_overlap<T>(old: &[Token<T>], new: &[Token<T>]) -> usize
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where
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T: PartialEq + Clone,
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{
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let minimum_offset = old.len().saturating_sub(new.len());
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for offset in minimum_offset..old.len() {
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if old.iter().skip(offset).zip(new.iter()).all(|(a, b)| a == b) {
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return offset;
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}
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}
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old.len()
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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use pretty_assertions::assert_eq;
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#[test]
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fn test_common_overlap() {
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assert_eq!(find_common_overlap(&["".into()], &["".into()]), 0);
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assert_eq!(
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find_common_overlap(
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&["a".into(), "b".into(), "c".into()],
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&["b".into(), "c".into(), "a".into()]
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),
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1
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);
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assert_eq!(
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find_common_overlap(
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&["a".into(), "a".into(), "a".into()],
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&["a".into(), "b".into(), "c".into()]
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),
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2
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);
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assert_eq!(
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find_common_overlap(
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&["a".into(), "b".into(), "c".into()],
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&["d".into(), "e".into(), "a".into()]
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),
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3
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);
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assert_eq!(
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find_common_overlap(&["a".into(), "a".into()], &["a".into()]),
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1
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);
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}
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}
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