amend a couple of errors (wrong sorting for some strings), and add todo for bug discovered
This commit is contained in:
@@ -211,14 +211,17 @@ struct
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( insKey
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, insIdx
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, splitTrieKeyStart
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, splitTrieKeyEnd
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, trieChild
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, childKeys
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, childChildren
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, parentKeys
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, parentChildren
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, parentConstructor
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) =
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let
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(* child node should always have CHILDREN case,
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* because we are splitting prefix into two,
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* when neither trieKey nor insKey match the prefix. *)
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val childNode = CHILDREN {keys = childKeys, children = childChildren}
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val keys =
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Vector.mapi
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@@ -228,16 +231,10 @@ struct
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val children =
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Vector.mapi (fn (idx, elt) => if idx <> insIdx then elt else childNode)
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parentChildren
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in
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CHILDREN {keys = keys, children = children}
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parentConstructor {keys = keys, children = children}
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end
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(*
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* todo:
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* - Complete code for FOUND_WITH_CHILDREN case in insert function.
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*)
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fun insertNewChild (keys, insIdx, insKey, children, constructor) =
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let
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val newLength = Vector.length keys + 1
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@@ -250,7 +247,6 @@ struct
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if idx < insIdx then Vector.sub (children, idx)
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else if idx > insIdx then Vector.sub (children, idx - 1)
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else FOUND)
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in
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constructor {keys = newKeys, children = newChildren}
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end
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@@ -263,6 +259,99 @@ struct
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constructor {keys = newKeys, children = newChildren}
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end
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fun foundInsertPos
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(keys, children, keyPos, insKey, insIdx, trie, helpInsert, constructor) =
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let
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val trieKey = Vector.sub (keys, insIdx)
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val nextKeyPos = keyPos + 1
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in
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(case insertKeyMatch (insKey, trieKey, nextKeyPos) of
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(* may need to split string if difference found but prefix matched *)
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DIFFERENCE_FOUND_AT diffIdx =>
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let
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val splitTrieKeyStart = String.substring (trieKey, 0, diffIdx)
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val trieChild = Vector.sub (children, insIdx)
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in
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if
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String.sub (trieKey, diffIdx)
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> String.sub (insKey, diffIdx)
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then
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(* place insKey before trieKey *)
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let
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val childKeys = Vector.fromList [insKey, trieKey]
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val childChildren = Vector.fromList [FOUND, trieChild]
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in
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insertDifferenceFoundAt
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( insKey
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, insIdx
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, splitTrieKeyStart
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, trieChild
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, childKeys
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, childChildren
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, keys
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, children
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, constructor
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)
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end
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else
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(* place trieKey before insKey *)
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let
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val childKeys = Vector.fromList [trieKey, insKey]
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val childChildren = Vector.fromList [trieChild, FOUND]
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in
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insertDifferenceFoundAt
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( insKey
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, insIdx
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, splitTrieKeyStart
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, trieChild
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, childKeys
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, childChildren
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, keys
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, children
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, constructor
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)
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end
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end
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(* may not need to do anything if insert key matched,
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* as this is a set where only strings are stored.
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* however, if this is a non-found node, then I need to change
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* the tag/case. *)
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| FULL_INSERT_MATCH =>
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(* in case of a full match,
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* returned node should always be FOUND_WITH_CHILDREN,
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* because full match means this key was inserted into the trie. *)
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FOUND_WITH_CHILDREN {keys = keys, children = children}
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(* if insert key contains trie key, need to recurse down node *)
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| INSERT_KEY_CONTAINS_TRIE_KEY =>
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let val trieChild = Vector.sub (children, insIdx)
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in helpInsert (insKey, keyPos + String.size trieKey, trieChild)
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end
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(* if trie key contains insert key, need to split node *)
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| TRIE_KEY_CONTAINS_INSERT_KEY =>
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let
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val trieChild = Vector.sub (children, insIdx)
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val newKeys =
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Vector.mapi
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(fn (idx, key) => if idx <> insIdx then insKey else key) keys
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(* newTrieChild should always be FOUND_WITH_CHILDREN,
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* because previous part matches insert key,
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* and esecond part matches trieKey *)
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val newTrieChild = FOUND_WITH_CHILDREN
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{ keys = Vector.fromList [trieKey]
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, children = Vector.fromList [trieChild]
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}
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val newChildren =
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Vector.mapi
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(fn (idx, elt) => if idx <> insIdx then elt else newTrieChild)
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children
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in
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constructor {keys = newKeys, children = newChildren}
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end
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| NO_INSERT_MATCH => trie)
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end
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fun helpInsert (insKey, keyPos, trie) : t =
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case trie of
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FOUND =>
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@@ -281,108 +370,16 @@ struct
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INSERT_NEW_CHILD insIdx =>
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insertNewChild (keys, insIdx, insKey, children, CHILDREN)
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| FOUND_INSERT_POS insIdx =>
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let
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val trieKey = Vector.sub (keys, insIdx)
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val nextKeyPos = keyPos + 1
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in
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(case insertKeyMatch (insKey, trieKey, nextKeyPos) of
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NO_INSERT_MATCH => trie
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(* may need to split string if difference found but prefix matched *)
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| DIFFERENCE_FOUND_AT diffIdx =>
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let
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val splitTrieKeyStart =
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String.substring (trieKey, 0, diffIdx)
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val splitTrieKeyEnd = String.substring
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(trieKey, diffIdx, String.size trieKey - diffIdx)
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val trieChild = Vector.sub (children, insIdx)
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in
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if
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String.sub (trieKey, nextKeyPos)
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> String.sub (insKey, nextKeyPos)
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then
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(* place insKey before trieKey *)
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let
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val childKeys =
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Vector.fromList [insKey, splitTrieKeyEnd]
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val childChildren =
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Vector.fromList [FOUND, trieChild]
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in
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insertDifferenceFoundAt
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( insKey
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, insIdx
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, splitTrieKeyStart
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, splitTrieKeyEnd
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, trieChild
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, childKeys
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, childChildren
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, keys
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, children
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)
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end
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else
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(* place trieKey before insKey *)
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let
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val childKeys =
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Vector.fromList [splitTrieKeyEnd, insKey]
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val childChildren =
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Vector.fromList [trieChild, FOUND]
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in
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insertDifferenceFoundAt
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( insKey
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, insIdx
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, splitTrieKeyStart
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, splitTrieKeyEnd
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, trieChild
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, childKeys
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, childChildren
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, keys
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, children
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)
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end
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end
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(* may not need to do anything if insert key matched,
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* as this is a set where only strings are stored.
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* however, if this is a non-found node, then I need to change
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* the tag/case. *)
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| FULL_INSERT_MATCH =>
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FOUND_WITH_CHILDREN {keys = keys, children = children}
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(* if insert key contains trie key, need to recurse down node *)
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| INSERT_KEY_CONTAINS_TRIE_KEY =>
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let
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val trieChild = Vector.sub (children, insIdx)
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in
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helpInsert
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(insKey, keyPos + String.size trieKey, trieChild)
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end
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(* if trie key contains insert key, need to split node *)
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| TRIE_KEY_CONTAINS_INSERT_KEY =>
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let
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val trieChild = Vector.sub (children, insIdx)
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val newKeys =
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Vector.mapi
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(fn (idx, key) =>
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if idx <> insIdx then insKey else key) keys
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val splitTrieKeyEnd = String.substring
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( trieKey
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, String.size insKey
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, String.size trieKey - String.size insKey
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)
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val newTrieChild = FOUND_WITH_CHILDREN
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{ keys = Vector.fromList [splitTrieKeyEnd]
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, children = Vector.fromList [trieChild]
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}
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val newChildren =
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Vector.mapi
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(fn (idx, elt) =>
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if idx <> insIdx then elt else newTrieChild)
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children
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in
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CHILDREN {keys = newKeys, children = newChildren}
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end)
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end
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foundInsertPos
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( keys
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, children
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, keyPos
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, insKey
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, insIdx
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, trie
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, helpInsert
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, CHILDREN
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)
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| APPEND_NEW_CHILD =>
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appendNewChild (keys, insKey, children, CHILDREN))
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end
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@@ -394,7 +391,17 @@ struct
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INSERT_NEW_CHILD insIdx =>
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insertNewChild
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(keys, insIdx, insKey, children, FOUND_WITH_CHILDREN)
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| FOUND_INSERT_POS insIdx => raise Empty
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| FOUND_INSERT_POS insIdx =>
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foundInsertPos
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( keys
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, children
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, keyPos
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, insKey
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, insIdx
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, trie
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, helpInsert
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, FOUND_WITH_CHILDREN
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)
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| APPEND_NEW_CHILD =>
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appendNewChild (keys, insKey, children, FOUND_WITH_CHILDREN))
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end
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@@ -403,7 +410,11 @@ struct
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if String.size insKey > 0 then helpInsert (insKey, 0, trie) else trie
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fun fromString str =
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CHILDREN {keys = Vector.fromList [str], children = Vector.fromList [FOUND]}
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if String.size str > 0 then
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CHILDREN
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{keys = Vector.fromList [str], children = Vector.fromList [FOUND]}
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else
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raise Empty
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fun helpAddList (str, acc) = insert (str, acc)
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@@ -416,5 +427,16 @@ struct
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end
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| fromList ([]) = raise Empty
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val trie = fromList ["hello", "bye", "try", "why"]
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(* test trie *)
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val trie = fromList
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["hello", "hi", "bye", "below", "tree", "try", "why", "what"]
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(*
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* todo:
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* Insertion function works (and seems to work exactly as intended),
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* but there seems to be a problem with the 'exists' function,
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* because some strings ("try" and "why") are correctly stored
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* in the trie, as shown by the REPL,
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* but 'exists' for them returns false.
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*)
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end
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