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0 pointsmaleldil6mo ago0 comments

Not in Go. Empty slices and empty maps are nil, so it's ambiguous.

0 comments

To be precise.. empty slices and maps sometimes behave like nil (len, range etc) and sometimes not (inserting into a nil map). The former is a neat convenience, and I think extending that to JSON marshaling makes sense.

stackedinserter6mo ago

No, empty slices and empty maps in Go are not nil.

maleldilOP6mo ago

This is the idiomatic way of declaring empty slices in Go, and it prints true:

    var slice []string
    fmt.Println(slice == nil)

everybodyknows6mo ago

Whether to judge the line below idiomatic, or not, is a question I leave to the authorities -- but it is highly convenient, and prints "false".

  slice := []string{}
  fmt.Println(slice == nil)

tux36mo ago

This is indeed a nil slice, and it does have len() == 0, but Go also has a concept of empty slices separate from nil slices

The language just has a bad habit of confusing them some of the time, but not consistently, so you can still occasionally get bit by the difference

As someone who uses Go a lot, it's just one of those things...

stackedinserter6mo ago

Yes because it's nil. You declared it but not created. Same for map. Same for var something *string

j / k navigate · click thread line to collapse

0 comments

rowanseymour6mo ago

stackedinserter6mo ago

No, empty slices and empty maps in Go are not nil.

maleldilOP6mo ago

This is the idiomatic way of declaring empty slices in Go, and it prints true:

    var slice []string
    fmt.Println(slice == nil)

everybodyknows6mo ago

Whether to judge the line below idiomatic, or not, is a question I leave to the authorities -- but it is highly convenient, and prints "false".

  slice := []string{}
  fmt.Println(slice == nil)

tux36mo ago

This is indeed a nil slice, and it does have len() == 0, but Go also has a concept of empty slices separate from nil slices

The language just has a bad habit of confusing them some of the time, but not consistently, so you can still occasionally get bit by the difference

As someone who uses Go a lot, it's just one of those things...

stackedinserter6mo ago

Yes because it's nil. You declared it but not created. Same for map. Same for var something *string

j / k navigate · click thread line to collapse