35 lines
1003 B
Rust
35 lines
1003 B
Rust
//! Join hashmaps with a callback for merging or failing on conflicting keys.
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use std::hash::Hash;
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use hashbrown::HashMap;
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use never::Never;
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/// Combine two hashmaps via an infallible value merger. See also
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/// [try_join_maps]
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pub fn join_maps<K: Eq + Hash, V>(
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left: HashMap<K, V>,
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right: HashMap<K, V>,
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mut merge: impl FnMut(&K, V, V) -> V,
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) -> HashMap<K, V> {
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try_join_maps(left, right, |k, l, r| Ok(merge(k, l, r))).unwrap_or_else(|e: Never| match e {})
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}
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/// Combine two hashmaps via a fallible value merger. See also [join_maps]
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pub fn try_join_maps<K: Eq + Hash, V, E>(
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left: HashMap<K, V>,
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mut right: HashMap<K, V>,
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mut merge: impl FnMut(&K, V, V) -> Result<V, E>,
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) -> Result<HashMap<K, V>, E> {
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let mut mixed = HashMap::with_capacity(left.len() + right.len());
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for (key, lval) in left {
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let val = match right.remove(&key) {
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None => lval,
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Some(rval) => merge(&key, lval, rval)?,
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};
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mixed.insert(key, val);
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}
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mixed.extend(right);
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Ok(mixed)
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}
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