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fix error with 'helpExists' function; the error was that we recursed in 'helpExists' function by calling keyPos + 1 (nextKeyPos) which is the wrong way to search when the trie key has a string size larger than 1

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Humza Shahid
2024-09-04 13:32:45 +01:00
parent 6696480a39
commit 65eff83c0b
1 changed files with 15 additions and 22 deletions
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37
src/string-set.sml
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@@ -79,17 +79,19 @@ struct
SOME idx =>
let
val trieKey = Vector.sub (keys, idx)
val nextKeyPos = keyPos + 1
in
(case searchKeyMatch (searchKey, trieKey, nextKeyPos) of
(case searchKeyMatch (searchKey, trieKey, keyPos + 1) of
NO_SEARCH_MATCH => false
| FULL_SEARCH_MATCH =>
let val trieChild = Vector.sub (children, idx)
in isFoundNode trieChild
end
| SEARCH_KEY_CONTAINS_TRIE_KEY =>
let val trieChild = Vector.sub (children, idx)
in helpExists (searchKey, nextKeyPos, trieChild)
let
val trieChild = Vector.sub (children, idx)
in
helpExists
(searchKey, keyPos + String.size trieKey, trieChild)
end
| TRIE_KEY_CONTAINS_SEARCH_KEY => false)
end
@@ -103,17 +105,19 @@ struct
SOME idx =>
let
val trieKey = Vector.sub (keys, idx)
val nextKeyPos = keyPos + 1
in
(case searchKeyMatch (searchKey, trieKey, nextKeyPos) of
(case searchKeyMatch (searchKey, trieKey, keyPos + 1) of
NO_SEARCH_MATCH => false
| FULL_SEARCH_MATCH =>
let val trieChild = Vector.sub (children, idx)
in isFoundNode trieChild
end
| SEARCH_KEY_CONTAINS_TRIE_KEY =>
let val trieChild = Vector.sub (children, idx)
in helpExists (searchKey, nextKeyPos, trieChild)
let
val trieChild = Vector.sub (children, idx)
in
helpExists
(searchKey, keyPos + String.size trieKey, trieChild)
end
| TRIE_KEY_CONTAINS_SEARCH_KEY => false)
end
@@ -272,10 +276,7 @@ struct
val splitTrieKeyStart = String.substring (trieKey, 0, diffIdx)
val trieChild = Vector.sub (children, insIdx)
in
if
String.sub (trieKey, diffIdx)
> String.sub (insKey, diffIdx)
then
if String.sub (trieKey, diffIdx) > String.sub (insKey, diffIdx) then
(* place insKey before trieKey *)
let
val childKeys = Vector.fromList [insKey, trieKey]
@@ -427,16 +428,8 @@ struct
end
| fromList ([]) = raise Empty
(* test trie *)
val trie = fromList
["hello", "hi", "bye", "below", "tree", "try", "why", "what"]
(*
(*
* todo:
* Insertion function works (and seems to work exactly as intended),
* but there seems to be a problem with the 'exists' function,
* because some strings ("try" and "why") are correctly stored
* in the trie, as shown by the REPL,
* but 'exists' for them returns false.
* Implement prefix searching, returning all keys that match a given string prefix.
*)
end