feature: Add inc_search_prefix.

Dependent on louds-rs child_to_ancestors PR.

Cargo.toml

@@ -12,7 +12,8 @@ categories = ["compression", "data-structures"]
 edition = "2021"
 
 [dependencies]
-louds-rs = "0.6"
+# louds-rs = "0.6"
+louds-rs = { path = "../louds-rs" }
 mem_dbg = { version = "0.1.4", optional = true }
 serde = { version = "1.0", features = ["derive"], optional = true }
 

src/inc_search.rs

@@ -38,7 +38,10 @@
 //!
 //! This means the above code restores the time complexity of _O(m log n)_ for
 //! the loop.
-use crate::map::Trie;
+use crate::{
+    map::Trie,
+    try_collect::{TryCollect, TryFromIterator},
+};
 use louds_rs::LoudsNodeNum;
 
 #[derive(Debug, Clone)]
@@ -181,6 +184,18 @@ impl<'a, Label: Ord, Value> IncSearch<'a, Label, Value> {
         self.trie.value(self.node)
     }
 
+    /// Return the current prefix for this search.
+    pub fn prefix<C, M>(&self) -> C
+    where
+        C: TryFromIterator<Label, M>,
+        Label: Clone,
+    {
+        let mut v: Vec<Label> = self.trie.child_to_ancestors(self.node)
+            .map(|node| self.trie.label(node).clone()).collect();
+        v.reverse();
+        v.into_iter().try_collect().expect("Could not collect")
+    }
+
     // This isn't actually possible.
     // /// Return the mutable value at current node. There should be one for any
     // /// node where `answer.is_match()` is true.
@@ -217,24 +232,38 @@ mod search_tests {
     fn inc_search() {
         let trie = build_trie();
         let mut search = trie.inc_search();
+        assert_eq!("", search.prefix::<String, _>());
         assert_eq!(None, search.query(&b'z'));
+        assert_eq!("", search.prefix::<String, _>());
         assert_eq!(Answer::PrefixAndMatch, search.query(&b'a').unwrap());
+        assert_eq!("a", search.prefix::<String, _>());
         assert_eq!(Answer::Prefix, search.query(&b'p').unwrap());
+        assert_eq!("ap", search.prefix::<String, _>());
         assert_eq!(Answer::PrefixAndMatch, search.query(&b'p').unwrap());
+        assert_eq!("app", search.prefix::<String, _>());
         assert_eq!(Answer::Prefix, search.query(&b'l').unwrap());
+        assert_eq!("appl", search.prefix::<String, _>());
         assert_eq!(Answer::Match, search.query(&b'e').unwrap());
+        assert_eq!("apple", search.prefix::<String, _>());
     }
 
     #[test]
     fn inc_search_value() {
         let trie = build_trie();
         let mut search = trie.inc_search();
+        assert_eq!("", search.prefix::<String, _>());
         assert_eq!(None, search.query(&b'z'));
+        assert_eq!("", search.prefix::<String, _>());
         assert_eq!(Answer::PrefixAndMatch, search.query(&b'a').unwrap());
+        assert_eq!("a", search.prefix::<String, _>());
         assert_eq!(Answer::Prefix, search.query(&b'p').unwrap());
+        assert_eq!("ap", search.prefix::<String, _>());
         assert_eq!(Answer::PrefixAndMatch, search.query(&b'p').unwrap());
+        assert_eq!("app", search.prefix::<String, _>());
         assert_eq!(Answer::Prefix, search.query(&b'l').unwrap());
+        assert_eq!("appl", search.prefix::<String, _>());
         assert_eq!(Answer::Match, search.query(&b'e').unwrap());
+        assert_eq!("apple", search.prefix::<String, _>());
         assert_eq!(Some(&2), search.value());
     }
 
@@ -243,10 +272,13 @@ mod search_tests {
         let trie = build_trie();
         let mut search = trie.inc_search();
         assert_eq!(Err(0), search.query_until("zoo"));
+        assert_eq!("", search.prefix::<String, _>());
         search.reset();
         assert_eq!(Err(1), search.query_until("blue"));
+        assert_eq!("b", search.prefix::<String, _>());
         search.reset();
         assert_eq!(Answer::Match, search.query_until("apple").unwrap());
+        assert_eq!("apple", search.prefix::<String, _>());
         assert_eq!(Some(&2), search.value());
     }
 

src/map/trie.rs

@@ -3,7 +3,7 @@ use super::Trie;
 use crate::inc_search::IncSearch;
 use crate::iter::{PostfixIter, PrefixIter, SearchIter};
 use crate::try_collect::{TryCollect, TryFromIterator};
-use louds_rs::{ChildNodeIter, LoudsNodeNum};
+use louds_rs::{ChildNodeIter, LoudsNodeNum, AncestorNodeIter};
 use std::iter::FromIterator;
 
 impl<Label: Ord, Value> Trie<Label, Value> {
@@ -210,6 +210,10 @@ impl<Label: Ord, Value> Trie<Label, Value> {
     pub(crate) fn value_mut(&mut self, node_num: LoudsNodeNum) -> Option<&mut Value> {
         self.trie_labels[(node_num.0 - 2) as usize].value.as_mut()
     }
+
+    pub (crate) fn child_to_ancestors(&self, node_num: LoudsNodeNum) -> AncestorNodeIter {
+        self.louds.child_to_ancestors(node_num)
+    }
 }
 
 impl<Label, Value, C> FromIterator<(C, Value)> for Trie<Label, Value>