Cynical Software

Go Arrays

Initialise

Fixed contents	n/a	var a = []int{1,2,3,4,5}	1 2 3 4 5
Fixed contents [alternative]	n/a	a := []int{1,2,3,4,5}	1 2 3 4 5

Insert

Prepend element 'e'	var a=[]int{2,3,4} var e=1	a=append([]int{e},a ...)	1 2 3 4
Append element 'e'	var a=[]int{1,2,3} var e=4;	a=append(a,e)	1 2 3 4
Insert element 'e' at index 'n'	var a=[]int{1,2,3,4,5} var e=666 var n=3	a=append(a[:n], append([]int{e}, a[n:] ...)...)	1 2 3 666 4 5
Prepend array 'b'	var a=[]int{1,2,3,4,5} var b=[]int{10,20,30}	a=append(b, a...);	10 20 30 1 2 3 4 5
Append array 'b'	var a=[]int{1,2,3,4,5} var b=[]int{10,20,30}	a=append(a,b...)	1 2 3 4 5 10 20 30
Insert array 'b' at index 'n'	var a=[]int{1,2,3,4,5} var b=[]int{10,20,30} var n=3	a=append(a[:n], append(b, a[n:]...)...)	1 2 3 10 20 30 4 5
Concatenate array 'a' and array 'b'	var a=[]int{1,2,3} var b=[]int{4,5,6}	var c=append(a,b...)	1 2 3 4 5 6

Overwrite

Overwrite first element	var a=[]int{1,2,3}	a[0]=666	666 2 3
Overwrite last element	var a=[]int{1,2,3}	a[len(a)-1]=666	1 2 666
Overwrite element at index 'n'	var a=[]int{1,2,3} var n=1	a[n]=666	1 666 3
Overwrite all elements	var a=[]int{1,2,3,4,5,6} var b=[]int{7,8,9}	a=b	7 8 9

Count

Length of array	var a=[]int{1,2,3}	var n=len(a)	3
Size of underlying storage	var a=[100]int{1,2,3}	var n=cap(a)	100

Retrieve by index

Retrieve first element	var a=[]int{1,2,3}	var e=a[0]	1
Retrieve last element	var a=[]int{1,2,3}	var e=a[len(a)-1]	3
Retrieve element 'n'	var a=[]int{1,2,3} var n=2	var e=a[n]	3

Remove by index

Remove element at index 'n'	var a=[]int{1,2,3,4,5} var n=2	a=append(a[:n], a[n+1:]...)	1 2 4 5
Remove elements in index range 'm' to 'n' (inclusive)	var a=[]int{1,2,3,4,5} var m=1 var n=3	a=append(a[:m], a[n+1:]...)	1 5
Remove elements from index 'n' onwards (inclusive)	var a=[]int{1,2,3,4,5} var n=3	a=a[:n]	1 2 3

Slice

Slice from index 'm' to 'n' (inclusive)	var a=[]int{1,2,3,4,5} var m=1 var n=3	a=a[m:n+1]	2 3 4
Slice from index 'n' onwards (inclusive)	var a=[]int{1,2,3,4,5} var n=2	a=a[n:]	3 4 5
Slice up to index 'n' (inclusive)	var a=[]int{1,2,3,4,5} var n=3	a=a[:n+1]	1 2 3 4

Iterate

Iterate over array 'a'

var a=[]int{1,2,3,4,5}
var b=[]int{}

for _,x := range a {
b=append(b,x*2)
}

2 4 6 8 10

Search

Test element 'e' 'is in' array	var a=[]int{1,2,3,4,5} var e=3	var t = ( sort.SearchInts(a, e) != len(a) )	1
Find index of unique element 'e'	var a=[]int{1,2,3,4,5} var e=3	var n = sort.SearchInts(a, e)	2

Sort

Sort in ascending order	var a=[]int{5,1,4,3,2}	sort.Ints(a)	1 2 3 4 5
Sort in ascending order [alternative]	var a=[]int{5,1,4,3,2}	sort.Sort(sort.IntSlice(a))	1 2 3 4 5
Sort in descending order	var a=[]int{5,1,4,3,2}	// "sort.Reverse" wraps existing interface // replacing Less with an inverse Less sort.Sort(sort.Reverse(sort.IntSlice(a)))	5 4 3 2 1
Sort in custom order	// The sort.Interface methods: // Len, Less and Swap type InReverse []int func (s InReverse) Len() int { return len(s) } func (s InReverse) Less(i, j int) bool { return s[i] > s[j] } func (s InReverse) Swap(i, j int) { s[i], s[j] = s[j], s[i] } var a=[]int{5,1,4,3,2}	sort.Sort(InReverse(a))	5 4 3 2 1
Reverse	var a=[]int{1,2,3,4,5}	for i := len(a)/2-1; i >= 0; i-- { opp := len(a)-1-i a[i], a[opp] = a[opp], a[i] }	5 4 3 2 1
Reverse [alternative]	var a=[]int{1,2,3,4,5}	for left, right := 0, len(a)-1; left < right; left, right = left+1, right-1 { a[left], a[right] = a[right], a[left] }	5 4 3 2 1

Use as a stack

Push element 'e'	var a=[]int{1,2,3,4,5} var e=666	a=append(a,e)	1 2 3 4 5 666
Pop next element	var a=[]int{1,2,3,4,5}	a=a[:len(a)-1]	1 2 3 4
Retrieve next element	var a=[]int{1,2,3,4,5}	var e=a[len(a)-1]	5

Use as a FIFO

Add element 'e'	var a=[]int{1,2,3,4,5} var e=666	a=append(a,e)	1 2 3 4 5 666
Remove next element	var a=[]int{1,2,3,4,5}	a=a[1:]	2 3 4 5
Retrieve next element	var a=[]int{1,2,3,4,5}	var e=a[0]	1

Compare

Test for equality (true)	var a=[]int{1,2,3,4,5} var b=[]int{1,2,3,4,5}	var t=reflect.DeepEqual(a,b)	1
Test for equality (false)	var a=[]int{1,2,3,4,5} var b=[]int{1,2,3,4,50}	var t=reflect.DeepEqual(a,b)	0