On Sun, Apr 21, 2019 at 9:02 PM Pat Farrell <pat22...@gmail.com> wrote:
> On Sunday, April 21, 2019 at 11:50:38 PM UTC-4, Kurtis Rader wrote:
>>
>> On Sun, Apr 21, 2019 at 8:37 PM Pat Farrell <pat2...@gmail.com> wrote:
>>
>>> I have a logic error in my calculation. I am getting -2147483648 in an
>>> int32
>>>
>>> A 2s-complement 32-bit int by definition can represent the range
>> [-2147483648, 2147483647]. The definition of MinInt32 as `-1 << 31`
>> presumes a 2s-complement representation. Also, given your problem statement
>> why didn't you just compare the value you're getting from your calculation
>> for equality to MinInt32 to confirm they are equal?
>>
>
> I tried comparing to MinInt32 and it was not equal.
> Is that an inclusive range or open? Since the number I was getting sure
> looks like your lower bound.
>
The range is inclusive on both sides (exclusive notation usually uses `(`)
and `)` on either side). When I compare that magic value to MinInt32 it
evaluates to true:
package main
import "math"
import "fmt"
func main() {
var i int32 = 2147483647;
fmt.Printf("%d\n", i);
print(i == math.MinInt32, "\n");
i = -2147483648;
fmt.Printf("%d\n", i);
print(i == math.MinInt32, "\n");
}
So I don't know why you didn't find them equal but it clearly suggests a
different bug in your code. Note that doing `i = 2147483648` causes the go
compiler to complain that `constant 2147483648 overflows int32` as expected.
--
Kurtis Rader
Caretaker of the exceptional canines Junior and Hank
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