353 lines
9.8 KiB
Standard ML
353 lines
9.8 KiB
Standard ML
datatype rope =
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N0 of string
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| N1 of rope
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| N2 of rope * int * int * rope
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| L2 of string * string
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| N3 of rope * rope * rope
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val target_length = 1024
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val empty = N0 ""
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fun of_string string = N0 string
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fun size rope =
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case rope of
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N0 s => String.size s
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| N1 t => size t
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| N2(_, lm, rm, _) => lm + rm
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| N3(t1, t2, t3) =>
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let
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val t1_size = size t1
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val t2_size = size t2
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val t3_size = size t3
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in
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t1_size + t2_size + t3_size
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end
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| _ => raise Empty
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fun root rope =
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case rope of
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L2(s1, s2) => N2(N0 s1, String.size s1, String.size s2, N0 s2)
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| N3(t1, t2, t3) =>
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let
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val t1_size = size t1
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val t2_size = size t2
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val left = N2(t1, t1_size, t2_size, t2)
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val left_size = t1_size + t2_size
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val t3_size = size t3
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in
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N2(left, left_size, t3_size, N1 t3)
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end
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| t => t
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fun n1 rope =
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case rope of
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L2(s1, s2) =>
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N2(N0 s1, String.size s1, String.size s2, N0 s2)
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| N3(t1, t2, t3) =>
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let
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val t1_size = size t1
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val t2_size = size t2
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val left = N2(t1, t1_size, t2_size, t2)
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val left_size = t1_size + t2_size
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val t3_size = size t3
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in
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N2(left, left_size, t3_size, t3)
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end
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| t => N1 t
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fun ins_n2_left left right =
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case (left, right) of
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(L2(s1, s2), t3) => N3(N0 s1, N0 s2, t3)
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| (N3(t1, t2, t3), N1 t4) =>
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let
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val t1_size = size t1
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val t2_size = size t2
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val left = N2(t1, t1_size, t2_size, t2)
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val left_size = t1_size + t2_size
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val t3_size = size t3
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val t4_size = size t4
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val right = N2(t3, t3_size, t4_size, t4)
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val right_size = t3_size + t4_size
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in
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N2(left, left_size, right_size, right)
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end
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| (N3(t1, t2, t3), t4 as N2 _) =>
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let
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val left = N2(t1, size t1, size t2, t2)
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in
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N3(left, N1 t3, t4)
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end
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| (N3(t1, t2, t3), t4) =>
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let
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val t1_size = size t1
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val t2_size = size t2
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val left = N2(t1, t1_size, t2_size, t2)
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val t3_size = size t3
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val t4_size = size t4
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val right = N2(t3, t3_size, t4_size, t4)
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val left_size = t1_size + t2_size
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val right_size = t3_size + t4_size
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in
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N2(left, left_size, right_size, right)
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end
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| (l, r) =>
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N2(l, size l, size r, r)
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fun ins_n2_right left right =
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case (left, right) of
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(t1, L2(s1, s2)) => N3(t1, N0 s1, N0 s2)
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| (N1 t1, N3(t2, t3, t4)) =>
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let
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val t1_size = size t1
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val t2_size = size t2
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val left = N2(t1, t1_size, t2_size, t2)
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val t3_size = size t3
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val t4_size = size t4
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val right = N2(t3, t3_size, t4_size, t4)
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val right_size = t3_size + t4_size
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val left_size = t1_size + t2_size
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in
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N2(left, left_size, right_size, right)
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end
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| (t1 as N2 _, N3(t2, t3, t4)) =>
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let
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val right = N2(t3, size t3, size t4, t4)
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in
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N3(t1, N1 t2, right)
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end
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| (l, r) =>
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N2(l, size l, size r, r)
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fun ins cur_index string rope =
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case rope of
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N0 str =>
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let
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val old_str_size = String.size str
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val ins_str_size = String.size string
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val total_str_size = old_str_size + ins_str_size
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val left_size = ins_str_size + cur_index
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val prefer_left = left_size <= target_length
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val right_size = ins_str_size - cur_index
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val prefer_right = right_size <= target_length
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in
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if cur_index <= 0 then
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if total_str_size <= target_length then
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N0(string ^ str)
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else L2(string, str)
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else if cur_index >= old_str_size then
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if total_str_size <= target_length then
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N0(str ^ string)
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else L2(str, string)
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else if total_str_size <= target_length then
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let
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val str1 = String.substring(str, 0, cur_index)
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val str3 = String.substring(str, cur_index, old_str_size - cur_index)
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in
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N0(String.concat [str1, string, str3])
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end
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else
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let
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val str1 = String.substring(str, 0, cur_index)
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val str3 = String.substring(str, cur_index, old_str_size - cur_index)
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in
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if prefer_left then
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L2(str1 ^ string, str3)
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else if prefer_right then
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L2(str1, string ^ str3)
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else
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N3(N0 str1, N0 string, N0 str3)
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end
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end
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| N1 t =>
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let
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val t = ins cur_index string t
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in
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n1 t
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end
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| N2(l, lm, _, r) =>
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if cur_index < lm then
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let
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val l = ins cur_index string l
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in
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ins_n2_left l r
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end
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else
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let
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val next_index = cur_index - lm
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val r = ins next_index string r
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in
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ins_n2_right l r
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end
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| _ => raise Empty
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fun insert index string rope =
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let
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val rope = ins index string rope
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in
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root rope
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end
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fun sub start_idx end_idx acc rope =
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case rope of
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N0 str =>
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let
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val str_size = String.size str
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val before_start = start_idx <= 0
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val after_start = start_idx >= 0
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val after_end = end_idx >= str_size
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val before_end = end_idx <= str_size
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in
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if before_start andalso after_end then
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(str :: acc)
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else if after_start andalso before_start then
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let
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val len = end_idx - start_idx
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val str = String.substring(str, start_idx, len)
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in
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(str :: acc)
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end
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else if after_start andalso after_end then
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let
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val len = str_size - start_idx
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val str = String.substring(str, start_idx, len)
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in
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(str :: acc)
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end
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else
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let
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val str = String.substring(str, 0, end_idx)
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in
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(str::acc)
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end
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end
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| N1 t =>
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sub start_idx end_idx acc t
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| N2(l, lm, _, r) =>
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let
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val starts_before = lm > start_idx
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val ends_before = lm > end_idx
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val starts_after = lm < start_idx
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val ends_after = lm < end_idx
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in
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if starts_before andalso ends_before then
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sub start_idx end_idx acc l
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else if starts_after andalso ends_after then
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let
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val next_start = start_idx - lm
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val next_end = end_idx - lm
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in
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sub next_start next_end acc r
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end
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else
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let
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val next_start = start_idx - lm
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val next_end = end_idx - lm
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val sub_acc = sub next_start next_end acc r
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in
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sub start_idx end_idx sub_acc l
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end
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end
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| _ => raise Empty
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fun substring start length rope =
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let
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val finish = start + length
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val lst = sub start finish [] rope
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in
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String.concat lst
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end
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fun del start_idx end_idx rope =
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case rope of
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N0 str =>
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let
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val str_size = String.size str
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val before_start = start_idx <= 0
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val after_end = end_idx >= str_size
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val after_start = start_idx >= 0
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val before_end = end_idx <= str_size
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in
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if before_start andalso after_end then
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(N0 "", false)
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else if after_start andalso before_end then
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let
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val str1 = String.substring(str, 0, start_idx)
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val del_len = str_size - end_idx
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val str2 = String.substring(str, start_idx, del_len)
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val new_len = str_size - del_len
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in
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if new_len <= target_length then
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(N0(str1 ^ str2), false)
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else
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(L2(str1, str2), true)
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end
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else if after_start andalso after_end then
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let
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val str = String.substring(str, 0, start_idx)
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in
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(N0 str, false)
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end
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else
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let
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val len = str_size - end_idx
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val str = String.substring(str, end_idx, len)
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in
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(N0 str, false)
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end
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end
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| N1 t =>
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let
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val (t, did_ins) = del start_idx end_idx t
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val t = if did_ins then n1 t else t
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in
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(t, did_ins)
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end
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| N2(l, lm, rm, r) =>
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let
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val start_is_less = lm > start_idx
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val end_is_less = lm > end_idx
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val start_is_more = lm < start_idx
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val end_is_more = lm < end_idx
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in
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if start_is_less andalso end_is_less then
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let
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val (l, did_ins) = del start_idx end_idx l
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in
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case did_ins of
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false =>
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(N2(l, size l, rm, r), false)
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| true =>
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(ins_n2_left l r, true)
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end
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else if start_is_more andalso end_is_more then
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let
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val next_start = start_idx - lm
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val next_end = end_idx - lm
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val (r, did_ins) = del next_start next_end r
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in
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case did_ins of
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false =>
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(N2(l, lm, size r, r), false)
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| true =>
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(ins_n2_right l r, true)
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end
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else
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let
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val (l, did_ins_l) = del start_idx end_idx l
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val r_start = start_idx - lm
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val r_end = end_idx - lm
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val (r, did_ins_r) = del r_start r_end r
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in
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if did_ins_l then
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(ins_n2_left l r, true)
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else if did_ins_r then
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(ins_n2_right l r, true)
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else
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(N2(l, size l, size r, r), false)
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end
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end
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| _ => raise Empty
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