Go rune type explanation

Question

I have found rune type in Go and have a simple question but worth an explnation.

I fount that it is an alias for int32 and purpose is to distinguish number and character values.

But I am confused with the term "rune" what actually it stands for ? e.g uint == unsigned int

score 11 · Accepted Answer · answered Jul 25 '13 at 11:09

11

But I am confused with the term "rune" what actually it stands for ? e.g uint == unsigned int

Rune stands for letter. ("Runes" are the letters in a set of related alphabets known as runic alphabets, which were used to write various Germanic languages before the adoption of the Latin alphabet. [Wikipedia]).

If a variable has type rune in Go you know it is intended to hold a unicode code point. (rune is shorter and clearer than codepoint). But it is technical a int32, i.e. its representation in memory is that of an int32.

answered Jul 25 '13 at 11:09

Volker

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http://en.wikipedia.org/wiki/Runes - ideal for Lord of the Rings fans :-P And the old English Þ thorn letter, still in use in Iceland, has a runic counterpart. – Rick-777 Jul 25 '13 at 20:26
But there are codepoints for non-Runic alphabets (e.g. the CJK extensions: http://unicode.org/charts/). To call a 32-bit codepoint a "rune" seems quite misleading to me. – aschmied Dec 04 '17 at 15:07

score 6 · Answer 2 · answered Jul 25 '13 at 10:57

In the general sense, Unicode "rune" is just a number, exactly like 64(0x40) is the number which is the code for '@' in both ASCII and Unicode.

Is 64 a real number? Yes, of course. you can assign literal 64 to a float variable.
Is 64 an integral number? Yes. You can assign literal 64 to any integral variable.
Is 64 a signed number? Yes. You can assing literal 64 to any unsigned variable.
Is 64 an unsigned number? Yes. You can assign literal 64 to any signed variable.

package main

import "fmt"

func main() {
    var f float64
    f = 64
    var b int8
    b = 64
    var u uint16
    u = 64
    var i int
    i = 64
    fmt.Println(f, b, u, i)

}

Playground

Output:

64 64 64 64

What this attempts to show is that [small] whole numbers (as well as such literals) are basically typeless, i.e. untyped.

Related: Rune Literals.

Go rune type explanation

2 Answers2

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