How Do I Accurately Count Non-Zero Elements in a Go Array?

Counting Elements in an Array in Go

In Go, arrays are fixed in size and cannot be resized dynamically. The length of an array is an intrinsic property of its type. Therefore, the common approach of using the len() function, as illustrated in the provided code snippet, retrieves the declared size of the array rather than the number of items currently set.

In Go, array elements are initialized to their zero value upon creation. For example, an array of integers will have all its elements initialized to 0, while an array of booleans will be initialized to false. Thus, the "total items in array," which in this context refers to the number of non-zero elements, is always equal to the array length.

The Go specification explicitly states, "The length is part of the array's type; it must evaluate to a non-negative constant representable by a value of type int. The length of array a can be discovered using the built-in function len()."

However, slices, which are dynamically-sized views of underlying arrays, provide a more flexible approach. A slice header contains a pointer to the base element in the array, a length representing the number of accessible elements, and a capacity indicating the maximum potential length. By utilizing slices, one can dynamically adjust the number of accessible elements within a contiguous segment of the underlying array.

For further understanding, refer to the following resources:

• The Go Blog: Go Slices: Usage and Internals
• The Go Blog: Arrays, Slices (and Strings): The Mechanics of 'append'

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