Slices, Maps and Pointers

Go provides three essential data structures beyond basic types: slices (dynamic arrays), maps (hash tables), and pointers (memory addresses). Understanding these is crucial for writing effective Go code.

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Arrays

Arrays in Go have a fixed size determined at compile time:

var a [5]int                    // [0, 0, 0, 0, 0]
b := [3]string{"a", "b", "c"}  // [a, b, c]
c := [...]int{1, 2, 3, 4}      // size inferred: [1, 2, 3, 4]

Arrays are rarely used directly in Go because their size is part of the type — [3]int and [5]int are different types. Use slices instead.

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Slices

A slice is a dynamically-sized, flexible view into an underlying array. Slices are Go's most commonly used data structure.

Creating Slices

// Slice literal
nums := []int{1, 2, 3, 4, 5}

// make(type, length, capacity)
s := make([]int, 5)       // len=5, cap=5, all zeros
s := make([]int, 0, 10)   // len=0, cap=10, empty but pre-allocated

// Nil slice
var s []int                // nil, len=0, cap=0

Slice Internals

A slice is a three-field struct internally: