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use joinEndOfLeft and joinStartOfRight functions to navigate between nodes in the gap buffer

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This commit is contained in:
Humza Shahid
2024-05-25 12:56:33 +01:00
parent 54b052c8f5
commit 153c66b546
3 changed files with 73 additions and 82 deletions
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66
gap_buffer.sml
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@@ -36,15 +36,6 @@ struct
fun isThreeLessThanTarget (s1, s2, s3) =
String.size s1 + String.size s2 + String.size s3 <= targetLength
local
fun helpCalcIndex (left, total) =
case left of
[] => total
| hd :: tail => helpCalcIndex (tail, total + String.size hd)
in
fun calcIndex left = helpCalcIndex (left, 0)
end
fun consLeft (curIdx, newString, left, right) =
{ idx = curIdx + String.size newString
, left = newString :: left
@@ -69,6 +60,20 @@ struct
| [] => consLeft (curIdx, newString, left, right))
| [] => consLeft (curIdx, newString, left, right)
fun joinEndOfLeft (newString, left) =
case left of
hd :: tail =>
if isLessThanTarget (newString, hd) then (hd ^ newString) :: tail
else newString :: left
| [] => newString :: left
fun joinStartOfRight (newString, right) =
case right of
hd :: tail =>
if isLessThanTarget (newString, hd) then (newString ^ hd) :: tail
else newString :: right
| [] => newString :: right
fun ins (idx, newString, curIdx, left, right) : t =
if curIdx = idx then
preferInsertLeft (curIdx, newString, left, right)
@@ -87,7 +92,7 @@ struct
then
(* The requested index is prior to the string on the left,
* so move leftward one string. *)
ins (idx, newString, prevIdx, tail, hd :: right)
ins (idx, newString, prevIdx, tail, joinStartOfRight (hd, right))
else
(* The requested index is either:
* - At the start of the left string
@@ -96,13 +101,27 @@ struct
idx = prevIdx
then
(* At start of string. *)
if isLessThanTarget (newString, hd) then
{ idx = curIdx + String.size newString
, left = (newString ^ hd) :: tail
, right = right
}
else
{idx = prevIdx, left = tail, right = newString :: hd :: right}
{ idx = curIdx + String.size newString
, right = right
, left =
(* These two meant to look reversed,
* with respect to newString and hd.
*
* The line
* `newString ^ hd`
* places the contents of newString before hd,
* and the line
* `hd :: newString`
* in a zipper also places newString before hd.
*
* Using `newString ^ hd` with `newString :: hd` gives
* different contents in the case of a zipper.
* *)
if isLessThanTarget (newString, hd) then
(newString ^ hd) :: tail
else
hd :: newString :: tail
}
else
(* In middle of string. *)
let
@@ -119,7 +138,7 @@ struct
else if isLessThanTarget (sub1, newString) then
{ idx = prevIdx + String.size sub1 + String.size newString
, left = (sub1 ^ newString) :: tail
, right = sub2 :: right
, right = joinStartOfRight (sub2, right)
}
else if isLessThanTarget (newString, sub2) then
{ idx = prevIdx + String.size sub1
@@ -142,13 +161,16 @@ struct
val nextIdx = String.size hd + curIdx
in
if idx > nextIdx then
ins (idx, newString, nextIdx, hd :: left, tail)
ins (idx, newString, nextIdx, joinEndOfLeft (hd, left), tail)
else if idx = nextIdx then
(* At end of next string. *)
if isLessThanTarget (newString, hd) then
{idx = curIdx, left = left, right = (hd ^ newString) :: tail}
else
{idx = curIdx, left = left, right = hd :: newString :: tail}
{ idx = curIdx
, left = left
, right = hd :: (joinStartOfRight (newString, tail))
}
else
let
val length = idx - curIdx
@@ -166,7 +188,7 @@ struct
else if isLessThanTarget (sub1, newString) then
{ idx = curIdx + String.size sub1 + String.size newString
, left = (sub1 ^ newString) :: left
, right = sub2 :: tail
, right = joinStartOfRight (sub2, tail)
}
else if isLessThanTarget (newString, sub2) then
{ idx = curIdx + String.size sub1
@@ -176,7 +198,7 @@ struct
else
{ idx = curIdx + String.size sub1 + String.size newString
, left = newString :: sub1 :: left
, right = sub2 :: tail
, right = joinStartOfRight (sub2, tail)
}
end
end