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begin implementation of PersistentVector.splitRight function

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This commit is contained in:
Humza Shahid
2026-01-16 21:58:59 +00:00
parent 08abb43e3b
commit eb316d7be2
1 changed files with 69 additions and 11 deletions
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80
fcore/persistent-vector.sml
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@@ -328,7 +328,7 @@ struct
loopPrevMatch (start, finish, tree, count - 1)
end
fun splitLeft (cursorIdx, tree) =
fun splitLeft (splitIdx, tree) =
case tree of
LEAF (items, sizes) =>
if Vector.length items = 0 then
@@ -338,20 +338,20 @@ struct
let
val {start, ...} = Vector.sub (items, 0)
in
(* if all items are after cursorIdx,
(* if all items are after splitIdx,
* then we want to return an empty tree,
* splitting everything *)
if cursorIdx < start then
if splitIdx < start then
empty
else if cursorIdx > Vector.sub (sizes, Vector.length sizes - 1) then
(* if all items are before cursorIdx,
else if splitIdx > Vector.sub (sizes, Vector.length sizes - 1) then
(* if all items are before splitIdx,
* then we want to return the same tree,
* splitting nothing *)
tree
else
(* we want to split from somewhere in middle, keeping left *)
let
val idx = BinSearch.equalOrMore (cursorIdx, sizes)
val idx = BinSearch.equalOrMore (splitIdx, sizes)
val idx = SOME idx
val items = VectorSlice.slice (items, 0, idx)
@@ -364,24 +364,24 @@ struct
end
end
| BRANCH (nodes, sizes) =>
if cursorIdx < Vector.sub (sizes, 0) then
if splitIdx < Vector.sub (sizes, 0) then
(* we want to split first node from rest *)
splitLeft (cursorIdx, Vector.sub (nodes, 0))
else if cursorIdx > Vector.sub (sizes, Vector.length sizes - 1) then
splitLeft (splitIdx, Vector.sub (nodes, 0))
else if splitIdx > Vector.sub (sizes, Vector.length sizes - 1) then
(* split point is after this subtree,
* so return this subtree unchanged *)
tree
else
(* we want to split from somewhere in middle *)
let
val idx = BinSearch.equalOrMore (cursorIdx, sizes)
val idx = BinSearch.equalOrMore (splitIdx, sizes)
val prevSize =
if idx = 0 then
0
else
Vector.sub (sizes, idx - 1)
val child =
splitLeft (cursorIdx - prevSize, Vector.sub (nodes, idx))
splitLeft (splitIdx - prevSize, Vector.sub (nodes, idx))
val sizes = VectorSlice.slice (sizes, 0, SOME idx)
val nodes = VectorSlice.slice (nodes, 0, SOME idx)
@@ -405,6 +405,64 @@ struct
end
end
(* When we split in this function,
* we always want to update the sizes vector
* so that the relative rope-like metadata is valid *)
fun splitRight (splitIdx, tree) =
case tree of
BRANCH (nodes, sizes) =>
if splitIdx > Vector.sub (sizes, Vector.length sizes - 1) then
(* splitIdx is greater than largest element,
* so we want to remove everything;
* or, in other words, we want to return an empty vec *)
empty
else
let
val idx = BinSearch.equalOrMore (splitIdx, sizes)
val prevSize =
if idx = 0 then
0
else
Vector.sub (sizes, idx - 1)
val oldChildSize = Vector.sub (sizes, idx)
val child = splitRight (splitIdx - prevSize, Vector.sub (nodes, idx))
val len = Vector.length nodes - (idx + 1)
val sizesSlice = VectorSlice.slice (sizes, idx + 1, SOME len)
val nodesSlice = VectorSlice.slice (nodes, idx + 1, SOME len)
in
if isEmpty child then
if VectorSlice.length sizesSlice = 0 then
(* if we descended down last node and last node became empty,
* then return empty vector *)
empty
else
let
val nodes = VectorSlice.vector nodesSlice
val sizes = VectorSlice.map (fn el => el - prevSize) sizesSlice
in
BRANCH (nodes, sizes)
end
else
let
val newChildSize = getFinishIdx child
val difference = oldChildSize - newChildSize
val sizes = Vector.tabulate (VectorSlice.length sizesSlice + 1,
fn i =>
if i = 0 then
newChildSize
else
VectorSlice.sub (sizesSlice, i - 1) - difference
)
val child = VectorSlice.full #[child]
val nodes = VectorSlice.concat [child, nodesSlice]
in
BRANCH (nodes, sizes)
end
end
(* functions only for testing *)
fun fromListLoop (lst, acc) =
case lst of