My fave golang slice trick is the len of an empty slice is 0, but the slice itself is == to nil, but the len of nil won't compile. Can't understand that one.
nil is not a value, it's a predeclared identifier.
it represents zero value for pointers, interfaces, maps, slices, channels and function types, representing an uninitialized value
len(nil) feels like it should work if you think of nil as the same as "value of empty array"
but what should be:
var p *Struct
len(p)
???
In languages with null and type inference, `var x = null` is probably not going to infer the type you want. In languages with function overloading (which is essentially the case for Go `len`), `f(null)` is going to be a compile-time error if multiple overloads are potentially null.
Of the various legitimate issues around nil (box vs. unboxed, nil receivers, nilability of all pointers), this is the most not-actually-ever-an-issue.
That’s not true. An empty slice is initialized: []T{} or make(T[]); it’s not equal to nil.[1] The zero value nil slice is technically not an “empty slice”. Colloquially you may call a nil slice an empty slice, but the nil-ness is still an important distinction that manifests in e.g. encoding/json.Marshal; nil marshals to null, whereas an initialized empty slice marshals to [].
If you want to test the emptiness of a slice, test the length, don’t compare it to nil.