Learning Golang fullsteam ahead

This isn't written in any real order and it won't have everything on these items until I actually need them. These are basically the notes that I did when I was learning this language.

Maps, Arrays, Slices

Arrays

var a1 [5]int; //array of 5 ints

• whatever isn't initialized is set to 0 in that type - 0 in int, empty '' in string, remember this as it might come up in loops

Slices are array without any size given, and so they can grow as needed

var s1 []int //empty slice with length 0
s2 := make([]string, 3) //if we want a slice with a starting length we need to use the make function, all elements are empty

• to add new values you use append

When using slices you can easily create a slice of a slice

s3 := s1[3:6] //from 3-rd to 6-th element of a slice - length of the new slice is 3, and the capacity is 6
s4 := s1[:3] //from the first element to the 3-rd
s5 := s1[3:] //from the third element to the end

• slices can have different capacities and length, they do not need to be always the same - using 3:6 creates a 3 lenthg slice with capacity of 6 - first 3 elements are empty

If you need you can use s1... to unpack the slice and get the straight values

Maps are basically associated arrays or dictionaries - key, value arrays

m1 := make(map[string]int) //string keys, int values
m1["one"] = 1

m2 := make(map[int][]string) //int keys, string array values
m2[1] = []string{ "chocolate" }

• you can delete stuff using delete(map, key)

You can access something that doesn't exist and it will return empty if that key doesn't exits - You can just access everything but here's the proper way

if value, ok : m2["four"]; ok {
    fmt.Println("key four found in array")
}

Maps use hashes internally and grow at 80% of fill where the memory is doubled and elements are incrementally copied over - I assume this means that maps might cause some small spikes in slow downs when setting up the doubled size. At least until now maps looked heavier than other types so it might be best to use them sparringly.

Sort Package

Go has a built in sort package go sort.Ints(slice1) or go sort.Slice(slice, func) - where in the second you pass a function that sort them based on whatever you assign - same as in php filter, sort, map. There also exists sort.Sort(structs) but you have to create a sort interface for that struct - basically add these 3 methods go Len(), Swap(i,j) Less(i,j) to the struct and it should work correctly.