A Go string is a read-only slice of bytes. The language
and the standard library treat strings specially - as
containers of text encoded in
UTF-8
.
In other languages, strings are made of “characters”.
In Go, the concept of a character is called a
rune
- it’s
an integer that represents a Unicode code point.
This Go blog post
is a good
introduction to the topic. | |
|  package main
|
| import (
"fmt"
"unicode/utf8"
)
|
| func main() {
|
s
is a
string
assigned a literal value
representing the word “hello” in the Thai
language. Go string literals are UTF-8
encoded text.
| const s = "สวัสดี"
|
Since strings are equivalent to
[]byte
, this
will produce the length of the raw bytes stored within. | fmt.Println("Len:", len(s))
|
Indexing into a string produces the raw byte values at
each index. This loop generates the hex values of all
the bytes that constitute the code points in
s
. | for i := 0; i < len(s); i++ {
fmt.Printf("%x ", s[i])
}
fmt.Println()
|
To count how many
runes
are in a string, we can use
the
utf8
package. Note that the run-time of
RuneCountInString
depends on the size of the string,
because it has to decode each UTF-8 rune sequentially.
Some Thai characters are represented by UTF-8 code points
that can span multiple bytes, so the result of this count
may be surprising. | fmt.Println("Rune count:", utf8.RuneCountInString(s))
|
A
range
loop handles strings specially and decodes
each
rune
along with its offset in the string. | for idx, runeValue := range s {
fmt.Printf("%#U starts at %d\n", runeValue, idx)
}
|
We can achieve the same iteration by using the
utf8.DecodeRuneInString
function explicitly. | fmt.Println("\nUsing DecodeRuneInString")
for i, w := 0, 0; i < len(s); i += w {
runeValue, width := utf8.DecodeRuneInString(s[i:])
fmt.Printf("%#U starts at %d\n", runeValue, i)
w = width
|
This demonstrates passing a
rune
value to a function. | examineRune(runeValue)
}
}
|
| func examineRune(r rune) {
|
Values enclosed in single quotes are
rune literals
. We
can compare a
rune
value to a rune literal directly. | if r == 't' {
fmt.Println("found tee")
} else if r == 'ส' {
fmt.Println("found so sua")
}
}
|