Go: What is the difference between slice and array?

Array — fixed-length, value-type, length in type. Slice — dynamic reference type backed by array.

Arrays are copied on assignment. Useful as map keys and for small fixed buffers.

1arr := [3]int{1, 2, 3}
2copy := arr  // full copy
3copy[0] = 99
4fmt.Println(arr[0])  // 1 — unchanged

Slices share backing memory. Mutations propagate. append may reallocate.

1xs := []int{1, 2, 3, 4}
2sub := xs[1:3]  // shares array
3sub[0] = 200
4fmt.Println(xs[1])  // 200 — shared

When to use:

• Array — small fixed buffers, map keys.
• Slice — default for all sequences.

Common mistakes:

• Not capturing append result.
• Shared backing array mutations.
• Passing large arrays by value.
• Comparing slices with ==.