迭代边界与数据类型相同 [英] Iteration boundaries same as data type's
问题描述
我有一个函数需要 min , max uint16
参数,并且在某个点迭代数值范围。但是,如果 max 碰巧是 2 ^ 16-1 (并且它是一个有效的用例),那么溢出会中断循环逻辑。以下是一个演示 uint8
问题的示例代码:
package main
importfmt
func iter(min,max uint8){
for i:= min; i <= max; i ++ {
fmt.Printf(%d,,i)
}
}
func main(){
iter(0,255 )
}
正如您所看到的,程序永远不会结束。在另一个问题上也提到了类似的问题,但解决方案恰好显示了我遇到的同样问题。
我现在的想法是将循环变量转换为 uint32
,与此类似:
$ (分钟);我< = uint16(最大); i ++ {
fmt.Printf(%d,,i)
}
}
func main(){
iter(0,255 )
}
然而,这似乎是一个笨拙的解决方案,这不会为 uint64
或最大的 uintN
类型工作。感觉就像我缺少一些非常基本的东西。指导?
我知道 Brad Fitz的Iter解决方案,但似乎增加了不必要的开销。这是真的吗?
例如,对于 uint8
,
包主
导入fmt
函数(min ,max uint8){
{
min,max:= uint(min),uint(max)
for i:= min; i <= max; i ++ {
fmt.Printf(%d,,i)
}
}
}
func main(){
iter(0,255)
}
对于 uint64 < code $,b
$输出:
$ b $ pre $
$ b $ $ b func iter(min,max uint64){
for i:= min; i <= max; i ++ {
fmt.Printf(%d,,i)
if i == max {
break
}
}
}
func main(){
iter(^ uint64(0)-2,^ uint64(0))
}
18446744073709551613,18446744073709551614,18446744073709551615
$ p
$ p $
附录:
包主
导入fmt
func iter(min,max uint64){
for i,next:= min,min <= max;下一个; i,next = i + 1,i< max {
fmt.Printf(%#016 [1] x,i)
}
fmt.Println()
}
func main(){
const maxUint64 = ^ uint64(0)
iter(0,3)
iter(10,9)
iter(maxUint64-2,maxUint64)
输出:
0x0000000000000000 0x0000000000000001 0x0000000000000002 0x0000000000000003
0xfffffffffffffffd 0xfffffffffffffffe 0xffffffffffffffff
A function I have takes min, max uint16
parameters and at some point iterates over the numeric range. However, if max happens to be 2^16-1 (and it is a valid use case), then overflow breaks the loop logic. Here is an example code demonstrating the problem with uint8
:
package main
import "fmt"
func iter(min, max uint8) {
for i := min; i <= max; i++ {
fmt.Printf("%d, ", i)
}
}
func main() {
iter(0, 255)
}
As you can see, the program never ends. A similar question was asked at another question but the solution exactly exhibits the same problem I have.
My thinking for now is to convert the loop variable to uint32
, similar to this:
package main
import "fmt"
func iter(min, max uint8) {
for i := uint16(min); i <= uint16(max); i++ {
fmt.Printf("%d, ", i)
}
}
func main() {
iter(0, 255)
}
However, this seems to be a clumsy solution, which is not going to work for uint64
or whatever biggest uintN
type. Feels like I am missing something very basic. Guidance?
I am aware of Brad Fitz's Iter solution, but it seems to add unneeded overhead. Is that true as well?
For example, for uint8
,
package main
import "fmt"
func iter(min, max uint8) {
{
min, max := uint(min), uint(max)
for i := min; i <= max; i++ {
fmt.Printf("%d, ", i)
}
}
}
func main() {
iter(0, 255)
}
For uint64
,
package main
import "fmt"
func iter(min, max uint64) {
for i := min; i <= max; i++ {
fmt.Printf("%d, ", i)
if i == max {
break
}
}
}
func main() {
iter(^uint64(0)-2, ^uint64(0))
}
Output:
18446744073709551613, 18446744073709551614, 18446744073709551615
Addendum:
Here's my version of Dave C's suggestion.
package main
import "fmt"
func iter(min, max uint64) {
for i, next := min, min <= max; next; i, next = i+1, i < max {
fmt.Printf("%#016[1]x ", i)
}
fmt.Println()
}
func main() {
const maxUint64 = ^uint64(0)
iter(0, 3)
iter(10, 9)
iter(maxUint64-2, maxUint64)
}
Output:
0x0000000000000000 0x0000000000000001 0x0000000000000002 0x0000000000000003
0xfffffffffffffffd 0xfffffffffffffffe 0xffffffffffffffff
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