Re: Question about ubyte x overflow, any safe way?
On Monday, 5 August 2019 at 18:21:36 UTC, matheus wrote: On Monday, 5 August 2019 at 01:41:06 UTC, Ali Çehreli wrote: ... Two examples with foreach and ranges. The 'ubyte.max + 1' expression is int. The compiler casts to ubyte (because we typed ubyte) in the foreach and we cast to ubyte in the range: ... Maybe it was a bad example of my part (Using for), and indeed using foreach would solve that specific issue, but what I'm really looking for if there is a flag or a way to check for overflow when assigning some variable. ubyte u = 260; // Here should be given some warning or throw exception. It's ubyte, but it could be any other data type. Yes, no question. It's checkedint that you should use. It was written exactly for that purpose.
Re: Question about ubyte x overflow, any safe way?
On Monday, 5 August 2019 at 01:41:06 UTC, Ali Çehreli wrote: ... Two examples with foreach and ranges. The 'ubyte.max + 1' expression is int. The compiler casts to ubyte (because we typed ubyte) in the foreach and we cast to ubyte in the range: ... Maybe it was a bad example of my part (Using for), and indeed using foreach would solve that specific issue, but what I'm really looking for if there is a flag or a way to check for overflow when assigning some variable. ubyte u = 260; // Here should be given some warning or throw exception. It's ubyte, but it could be any other data type. Thanks anyway, Matheus.
Re: Question about ubyte x overflow, any safe way?
On 08/04/2019 11:12 AM, matheus wrote:
Hi,
The snippet below will produce an "infinite loop" because obviously
"ubyte u" will overflow after 255:
import std.stdio;
void main(){
ubyte u = 250;
for(;u<256;++u){
writeln(u);
}
}
Question: Is there a way (Flag) to prevent this?
Matheus.
Two examples with foreach and ranges. The 'ubyte.max + 1' expression is
int. The compiler casts to ubyte (because we typed ubyte) in the foreach
and we cast to ubyte in the range:
void main() {
int count = 0;
// (Explicit request for) implicit conversion to ubyte
foreach (ubyte u; ubyte.min .. ubyte.max + 1) {
++count;
}
assert(count == 256);
import std.range;
import std.algorithm;
import std.conv;
int count2 = 0;
// Explicit conversion with to!ubyte
iota(ubyte.max + 1).map!(to!ubyte).each!(_ => ++count2);
assert(count2 == 256);
}
Ali
Re: Question about ubyte x overflow, any safe way?
On Sunday, 4 August 2019 at 18:38:34 UTC, Paul Backus wrote:
...
Use std.experimental.checkedint:
import std.stdio;
import std.experimental.checkedint;
void main()
{
for(Checked!(ubyte, Throw) u = ubyte(250); u < 256; ++u) {
writeln(u.get);
}
}
An exception will be thrown when you attempt to increment u
above 255.
Unfortunately I'm using DMD 2.072 which doesn't support this, but
I'll upgrade soon as I can and will check this out.
Thanks,
Matheus.
Re: Question about ubyte x overflow, any safe way?
On Sunday, 4 August 2019 at 18:22:30 UTC, matheus wrote: On Sunday, 4 August 2019 at 18:15:30 UTC, Max Haughton wrote: What do you want to do? If you just want to count to 255 then use a foreach This was just an example, what I'd like in this code is either: Get an error (exception) when overflow or even an warning (Only if "some" flag was active). If you want to prevent overflow you must either use BigInt or wrap ubyte in a struct that doesn't allow overflow Could you please elaborate about this struct wrapping? Do you mean manually check on change? Matheus. Std.experimental.checkedint maybe exactly what you are looking for
Re: Question about ubyte x overflow, any safe way?
On Sunday, 4 August 2019 at 18:22:30 UTC, matheus wrote:
On Sunday, 4 August 2019 at 18:15:30 UTC, Max Haughton wrote:
What do you want to do? If you just want to count to 255 then
use a foreach
This was just an example, what I'd like in this code is either:
Get an error (exception) when overflow or even an warning (Only
if "some" flag was active).
Use std.experimental.checkedint:
import std.stdio;
import std.experimental.checkedint;
void main()
{
for(Checked!(ubyte, Throw) u = ubyte(250); u < 256; ++u) {
writeln(u.get);
}
}
An exception will be thrown when you attempt to increment u above
255.
Re: Question about ubyte x overflow, any safe way?
On Sunday, 4 August 2019 at 18:15:30 UTC, Max Haughton wrote: What do you want to do? If you just want to count to 255 then use a foreach This was just an example, what I'd like in this code is either: Get an error (exception) when overflow or even an warning (Only if "some" flag was active). If you want to prevent overflow you must either use BigInt or wrap ubyte in a struct that doesn't allow overflow Could you please elaborate about this struct wrapping? Do you mean manually check on change? Matheus.
Re: Question about ubyte x overflow, any safe way?
On Sunday, 4 August 2019 at 18:12:48 UTC, matheus wrote:
Hi,
The snippet below will produce an "infinite loop" because
obviously "ubyte u" will overflow after 255:
import std.stdio;
void main(){
ubyte u = 250;
for(;u<256;++u){
writeln(u);
}
}
Question: Is there a way (Flag) to prevent this?
Matheus.
What do you want to do? If you just want to count to 255 then use
a foreach
If you want to prevent overflow you must either use BigInt or
wrap ubyte in a struct that doesn't allow overflow
