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Comments and style for rope

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This commit is contained in:
Zachary Yedidia
2016-03-18 21:25:45 -04:00
parent d55dabaa3b
commit cc098d05ef
2 changed files with 42 additions and 33 deletions
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65
rope.go
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@@ -1,31 +1,35 @@
package main
import (
// "fmt"
"math"
"unicode/utf8"
)
const (
ropeSplitLength = 1000
ropeJoinLength = 500
ropeRebalanceRatio = 1.2
// RopeSplitLength defines how large can a string be before it is split into two nodes
RopeSplitLength = 1000
// RopeJoinLength defines how short can a string be before it is joined
RopeJoinLength = 500
// RopeRebalanceRatio = 1.2
)
func min(a, b int) int {
// Min takes the min of two ints
func Min(a, b int) int {
if a > b {
return b
}
return a
}
func max(a, b int) int {
// Max takes the max of two ints
func Max(a, b int) int {
if a > b {
return a
}
return b
}
// A Rope is a data structure for efficiently manipulating large strings
type Rope struct {
left *Rope
right *Rope
@@ -35,28 +39,30 @@ type Rope struct {
len int
}
func newRope(str string) *Rope {
// NewRope returns a new rope from a given string
func NewRope(str string) *Rope {
r := new(Rope)
r.value = str
r.valueNil = false
r.len = utf8.RuneCountInString(r.value)
r.adjust()
r.Adjust()
return r
}
func (r *Rope) adjust() {
// Adjust modifies the rope so it is more balanced
func (r *Rope) Adjust() {
if !r.valueNil {
if r.len > ropeSplitLength {
if r.len > RopeSplitLength {
divide := int(math.Floor(float64(r.len) / 2))
r.left = newRope(r.value[:divide])
r.right = newRope(r.value[divide:])
r.left = NewRope(r.value[:divide])
r.right = NewRope(r.value[divide:])
r.valueNil = true
}
} else {
if r.len < ropeJoinLength {
r.value = r.left.toString() + r.right.toString()
if r.len < RopeJoinLength {
r.value = r.left.String() + r.right.String()
r.valueNil = false
r.left = nil
r.right = nil
@@ -64,36 +70,39 @@ func (r *Rope) adjust() {
}
}
func (r *Rope) toString() string {
// String returns the string representation of the rope
func (r *Rope) String() string {
if !r.valueNil {
return r.value
}
return r.left.toString() + r.right.toString()
return r.left.String() + r.right.String()
}
func (r *Rope) remove(start, end int) {
// Remove deletes a slice of the rope from start the to end (exclusive)
func (r *Rope) Remove(start, end int) {
if !r.valueNil {
r.value = string(append([]rune(r.value)[:start], []rune(r.value)[end:]...))
r.valueNil = false
r.len = utf8.RuneCountInString(r.value)
} else {
leftStart := min(start, r.left.len)
leftEnd := min(end, r.left.len)
rightStart := max(0, min(start-r.left.len, r.right.len))
rightEnd := max(0, min(end-r.left.len, r.right.len))
leftStart := Min(start, r.left.len)
leftEnd := Min(end, r.left.len)
rightStart := Max(0, Min(start-r.left.len, r.right.len))
rightEnd := Max(0, Min(end-r.left.len, r.right.len))
if leftStart < r.left.len {
r.left.remove(leftStart, leftEnd)
r.left.Remove(leftStart, leftEnd)
}
if rightEnd > 0 {
r.right.remove(rightStart, rightEnd)
r.right.Remove(rightStart, rightEnd)
}
r.len = r.left.len + r.right.len
}
r.adjust()
r.Adjust()
}
func (r *Rope) insert(pos int, value string) {
// Insert inserts a string into the rope at a specified position
func (r *Rope) Insert(pos int, value string) {
if !r.valueNil {
first := append([]rune(r.value)[:pos], []rune(value)...)
r.value = string(append(first, []rune(r.value)[pos:]...))
@@ -101,12 +110,12 @@ func (r *Rope) insert(pos int, value string) {
r.len = utf8.RuneCountInString(r.value)
} else {
if pos < r.left.len {
r.left.insert(pos, value)
r.left.Insert(pos, value)
r.len = r.left.len + r.right.len
} else {
r.right.insert(pos-r.left.len, value)
r.right.Insert(pos-r.left.len, value)
}
}
r.adjust()
r.Adjust()
}