add: slice internals backing array and slice header
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Inanc Gumus
@@ -1,44 +0,0 @@
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// For more tutorials: https://blog.learngoprogramming.com
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//
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// Copyright © 2018 Inanc Gumus
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// Learn Go Programming Course
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// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
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//
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package main
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import s "github.com/inancgumus/prettyslice"
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func main() {
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// ages, first and last2 have the same backing arrays
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ages := []int{35, 15, 25}
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first := ages[0:1]
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last2 := ages[1:3]
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ages[0] = 55
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ages[1] = 10
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ages[2] = 20
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// grades and ages have separate backing arrays
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grades := []int{70, 99}
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grades[0] = 50
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s.Show("ages", ages)
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s.Show("ages[0:1]", first)
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s.Show("ages[1:3]", last2)
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s.Show("grades", grades)
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// let's create a new scope
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// 'cause i'm going to use variables with the same name
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{
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// ages and agesArray have the same backing arrays
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agesArray := [3]int{35, 15, 25}
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ages := agesArray[0:3]
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ages[0] = 100
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ages[2] = 50
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s.Show("agesArray", agesArray[:])
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s.Show("agesArray's ages", ages)
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}
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}
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@@ -1,50 +0,0 @@
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// For more tutorials: https://blog.learngoprogramming.com
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//
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// Copyright © 2018 Inanc Gumus
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// Learn Go Programming Course
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// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
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//
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package main
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import (
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s "github.com/inancgumus/prettyslice"
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)
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func main() {
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// #1: arrays and non-empty slice literals create an array.
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// For the arrays, it's explicit, but for the slices,
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// it's done implicitly, behind the scenes.
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grades := [...]float64{40, 10, 20, 50, 60, 70} // #1
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// grades := []float64{40, 10, 20, 50, 60, 70} // #4
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// #5: let's break the connection
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// #6: comment-out
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// var newGrades []float64
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// newGrades = append(newGrades, grades...)
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// #6: shortcut: []float64(nil) is a nil float64 slice
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// newGrades := append([]float64(nil), grades...)
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// #2: cheap: slicing doesn't allocate new memory (array).
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// front := grades[:3]
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// front := newGrades[:3] // #5
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// #3: sort its first segment
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// sort.Float64s(front)
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// #7: new slices look at the same backing array
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// front, front2, front3, newGrades, they all have the same backing array
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// front2 := front[:3]
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// front3 := front
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s.PrintBacking = true // #1
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s.MaxPerLine = 7 // #1
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s.Show("grades", grades[:]) // #1
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// s.Show("newGrades", newGrades) // #5
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// s.Show("front", front) // #2
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// s.Show("front2", front2) // #7
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// s.Show("front3", front3) // #7
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}
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@@ -1,21 +0,0 @@
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// For more tutorials: https://blog.learngoprogramming.com
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//
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// Copyright © 2018 Inanc Gumus
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// Learn Go Programming Course
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// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
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//
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package main
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import s "github.com/inancgumus/prettyslice"
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func main() {
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ages := []int{35, 15, 25}
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first, last := ages[0:1], ages[1:3]
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s.Show("ages", ages)
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s.Show("first", first)
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s.Show("last", last)
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s.Show("nil slice", []int(nil))
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}
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@@ -1,61 +0,0 @@
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// For more tutorials: https://blog.learngoprogramming.com
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//
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// Copyright © 2018 Inanc Gumus
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// Learn Go Programming Course
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// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
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//
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package main
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import (
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"fmt"
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"unsafe"
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s "github.com/inancgumus/prettyslice"
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)
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// type collection [4]string // #1
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type collection []string // #2
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// go is pass by copy
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// only the slice header is copied: 3 integer fields (24 bytes)
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// think of passing an array with millions of elements.
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func main() {
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// SliceHeader lives here:
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// https://golang.org/src/runtime/slice.go
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s.PrintElementAddr = true
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// #1
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data := collection{"slices", "are", "awesome", "period", "!!" /* #5 */}
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// data := collection{"slices", "are", "awesome", "period", "!!"}
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change(data) // #1
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s.Show("main's data", data) // #1
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fmt.Printf("main's data slice's header: %p\n", &data) // #3
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// ----------------------------------------------------------------------
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// #4
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array := [...]string{"slices", "are", "awesome", "period", "!!" /* #5 */}
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// array's size depends on its elements
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fmt.Printf("array's size: %d bytes.\n", unsafe.Sizeof(array))
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// slice's size is always fixed: 24 bytes (on a 64-bit system) — slice value = slice header
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fmt.Printf("slice's size: %d bytes.\n", unsafe.Sizeof(data))
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}
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// #1
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// passed value will be copied in the function
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func change(data collection) {
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// data is a new variable inside the function:
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// var data collection
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data[2] = "brilliant!"
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s.Show("change's data", data)
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fmt.Printf("change's data slice's header: %p\n", &data) // #3
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}
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