The Go Programming Language

The size of an array is part of its type, so [3]int and [4]int are different types.

The size of an array is part of its type, so [3]int and [4]int are different types. The size must be a constant expression, that is, an expression whose value can be computed as the program is being compiled.

%x to print all the elements of an array or slice of bytes in hexadecimal, %t to show a boolean, and %T to display the type of a value.

Unlike arrays, slices are not comparable, so we cannot use == to test whether two slices contain the same elements. The standard library provides the highly optimized bytes.Equal function for comparing two slices of bytes ([]byte), but for other types of slice, we must do the comparison ourselves:

Under the hood, make creates an unnamed array variable and returns a slice of it; the array is accessible only through the returned slice. In the first form, the slice is a view of the entire array. In the second, the slice is a view of only the array’s first len elements, but its capacity includes the entire array. The additional elements are set aside for future growth.

For efficiency, the new array is usually somewhat larger than the minimum needed to hold x and y. Expanding the array by doubling its size at each expansion avoids an excessive number of allocations and ensures that appending a single element takes constant time on average. This program demonstrates the effect:

When you have a value of an interface type, you know nothing about what it is; you know only what it can do, or more precisely, what behaviors are provided by its methods.

Because the empty interface type places no demands on the types that satisfy it, we can assign any value to the empty interface.