background
Honeycomb Chief development evangelist Jessica stay Twitter A status message was posted on ：
fmt.Println("What is truth?", true)
can output:
What is truth? false
The execution result of the following code may be What is truth? false
fmt.Println("What is truth?", true)You can first think about the circumstances under which such a result will occur .
analysis
Let's look at the following code ：
// identifier.go
package main
import "fmt"
func main() {
true := false
fmt.Println(true)
}We think this code will compile and report errors , Or normal execution ？
The actual execution result is to print false, It will not compile and report errors .
So the code at the beginning of this article fmt.Println("What is truth?", true) It is possible to print What is truth? false Of .
Some students may be curious ？ Why is this so ？true No Go Keywords of language , Why can an identifier also be defined as true The variable of ？
The answer is ：true Not at all Go Keywords of language ,Go Language is currently only 25 Key words , As shown below ：
break default func interface select case defer go map struct chan else goto package switch const fallthrough if range type continue for import return var
these keyword Can't be used as Go Identifier of language .true yes Pre declaration identifier , It can be used as Go Identifier of language , The official instructions are as follows ：
Predeclared identifiers
The following identifiers are implicitly declared in the universe block:
Types: bool byte complex64 complex128 error float32 float64 int int8 int16 int32 int64 rune string uint uint8 uint16 uint32 uint64 uintptr Constants: true false iota Zero value: nil Functions: append cap close complex copy delete imag len make new panic print println real recover
therefore true := false Such code is in Go The language can be compiled normally , also go vet No potential errors will be detected .
not only true, All identifiers in the pre declaration identifier can be used as identifiers of global variables and local variables , Consider the following code ：
// identifier2.go
package main
import "fmt"
var nil = 100
var false = true
func main() {
true := false
fmt.Println(true, false, nil)
}You can think about the output ？
- A:
true false nil - B:
true false 100 - C:
true true 100 - D:
false true 100 - E:
false true nil
Those who want to know the answer can send messages to the official account. bsf Get answers .
summary
Go This feature of language has also attracted a lot of attention controversy , just as Go The error handling is the same .
We as users , We need to pay attention to ：Go Keywords are not allowed as identifiers , Others can be used as identifiers .
Open source address
Articles and sample code are open source GitHub: Go Primary language 、 Intermediate and advanced tutorials .
official account ：coding Advanced . Pay attention to the official account and get the latest information. Go Interview questions and technical stack .
Personal website ：Jincheng's Blog.
You know ： No taboo .
