N-dimensional arrays

March 1, 2023

There’s one sentence at the end of the paragraph yesterday about arrays, which I saved for today, as I think it deserves special attention:

Array types

Array types are always one-dimensional but may be composed to form multi-dimensional types.

[2][2][2]float64  // same as [2]([2]([2]float64))

The two examples provided do not represent a 2- and 3-dimensional array, therefore. Rather, they represent an array of arrays, and an array of arrays of arrays, respectively.

This might seem like a distinction without a difference, and if we were limited strictly to fixed-length arrays, it might be. But as we’ll see when we discuss the slice type next, we’ll see that this distinction actually makes a difference.

For now, though, just remember that there are no 2-, 3-, or higher-dimensional arrays in Go. Only one-dimensional arrays, which may in turn be of other 1-dimensional arrays, in effect, then, building up N-dimensionality.

Quotes from The Go Programming Language Specification, Version of January 19, 2023

Share this

Related Content

Empty structs

We finally we have enough knowledge for the EBNF format not to seem completely foreign, so let’s jump back and take a look at that, with the examples provided in the spec… Struct types … StructType = "struct" "{" { FieldDecl ";" } "}" . FieldDecl = (IdentifierList Type | EmbeddedField) [ Tag ] . EmbeddedField = [ "*" ] TypeName [ TypeArgs ] . Tag = string_lit . // An empty struct.

Struct tags

Struct types … A field declaration may be followed by an optional string literal tag, which becomes an attribute for all the fields in the corresponding field declaration. An empty tag string is equivalent to an absent tag. The tags are made visible through a reflection interface and take part in type identity for structs but are otherwise ignored. struct { x, y float64 "" // an empty tag string is like an absent tag name string "any string is permitted as a tag" _ [4]byte "ceci n'est pas un champ de structure" } // A struct corresponding to a TimeStamp protocol buffer.

Struct method promotion

Yesterday we saw an example of struct field promotion. But methods (which we haven’t really discussed yet) can also be promoted. Struct types … Given a struct type S and a named type T, promoted methods are included in the method set of the struct as follows: If S contains an embedded field T, the method sets of S and *S both include promoted methods with receiver T. The method set of *S also includes promoted methods with receiver *T.