Arithmetic expression in case

Getting Help
1

I want use case statement instead of switch for arithmetic comparison. Could you please let me know what’s wrong with the following code??

package main
import "fmt"
func main(){                                                                                                                                                            
        a := 2                                                                                                                                                                                                                                                                                                          
        switch a {                                                                                                                                                      
        case a < 5 :                                                                                                                                                    
                fmt.Println("value is less than 5")                                                                                                                               
        }                                                                                                                                                               
}
2

You can’t switch on expressions, only on constants. And you can’t switch on integers (see https://tour.golang.org/flowcontrol/9)

Do this:

package main

import "fmt"

func main() {
	a := 2
	if a < 5 {
		fmt.Println("value is less than 5")
	}
}
3

I just found the answer to my question over here

https://www.dotnetperls.com/switch-go

So my code would become,

package main
import "fmt"
func main(){
        a := 2
        switch {
        case a < 5 :
                fmt.Println("value is 2")
        }
}

This works

4

Be aware though, that this is only syntactic sugar for nested if/else statements, expressions are evaluated and compare in order given, there is no way the compiler were able to optimize that into a jump table.

2 Likes
5

Interesting, could you please provide some links supporting that?

I’ve never heard of jump table before, but just read now online, they say switch statements are relatively faster than if/else because of jump tables.

Blockquote

6

Switch beeing faster is only true when switching over a value rather than over expressions.

8

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