Another runnable example:
package main
const x = 8
var y = 8
var a byte = 1 << x / 2
var b byte = 1 << y / 2
func main() {
println(a) // 128
println(b) // 0
}
On Thursday, June 3, 2021 at 10:42:32 AM UTC-4 peterGo wrote:
> Jan,
>
> The untyped constant 1 assumes the type of x, which is float64. With
> explicit types:
>
> package main
>
> import "fmt"
>
> func main() {
> var a int = 0
> // invalid operation: float64(1) << a (shift of type float64)
> var x float64 = float64(1) << a
> fmt.Println(x)
> }
>
> https://play.golang.org/p/jQ4k5qrxcTu
>
> Peter
>
> On Thursday, June 3, 2021 at 5:52:23 AM UTC-4 Jan Mercl wrote:
>
>> On Thu, Jun 3, 2021 at 11:21 AM Brian Candler <b.ca...@pobox.com> wrote:
>> >
>> > Weird. It simplifies to this: https://play.golang.org/p/OsOhRMC6kBu
>>
>> I think this case is WAI.
>>
>> From https://golang.org/ref/spec#Operators
>>
>> " If the left operand of a non-constant shift expression is an untyped
>> constant, it is first implicitly converted to the type it would assume
>> if the shift expression were replaced by its left operand alone."
>>
>> The OP case is strange in that the constness of the RHS operator
>> somehow changes the interpretation of the above quotation
>> specification, but I cannot find that it should.
>>
>
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