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cmd/compile: Dividing complex128 by zero does not report an error #41308

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xiyichan opened this issue Sep 10, 2020 · 3 comments
Closed

cmd/compile: Dividing complex128 by zero does not report an error #41308

xiyichan opened this issue Sep 10, 2020 · 3 comments

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@xiyichan
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xiyichan commented Sep 10, 2020

What version of Go are you using (go version)?

$ go version
master

Does this issue reproduce with the latest release?

yes

What did you do?

package main
  
import (
     "fmt"
)
func main() {
    var x complex128 = complex(1, 2) // 1+2i
    fmt.Println(x/ 0)
}

What did you expect to see?

an error

What did you see instead?

image

@ianlancetaylor
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Please paste text as text, not as an image. Thanks.

This is expected behavior. In floating point arithmetic, dividing a finite value by zero gives you an infinity, not an error. See "Floating-point operators" at https://golang.org/ref/spec#Arithmetic_operators.

@xiyichan
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xiyichan commented Sep 10, 2020

package main

import (
	"testing"
)
func TestConstInt(t *testing.T){
	const x int =1
	t.Log(x/0)
}
func TestVarInt(t *testing.T){
	var x int =2
	t.Log(x/0)
}
func TestVarFloat64(t *testing.T){
	var x float64 =2.222
	t.Log(x/0)
}
func TestConstFloat64(t *testing.T){
	const x float64 =2.222
	t.Log(x/0)
}
func TestConstComplex(t *testing.T){
	const x complex128=complex(1,2)
	t.Log(x/0)
}
func TestVarComplex(t *testing.T){
	var x complex128=complex(1,2)
	t.Log(x/0)
}

This is the test code I wrote. Why use const to modify float64 and complex will cause errors.
@ianlancetaylor

@ianlancetaylor
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In Go, constant arithmetic does not use the same rules as variable arithmetic. In particular, constant floating point values have no infinity, or NaN, or negative zero. See https://golang.org/ref/spec#Constant_expressions .

In general for questions about the language it's better to use a forum. You will get better and faster answers. See https://golang.org/wiki/Questions.

@golang golang locked and limited conversation to collaborators Sep 10, 2021
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