Re: Wouldn't the compiler be smart with this shadowing variable?
On Saturday, 11 December 2021 at 20:22:13 UTC, frame wrote:
```d
// iteration works, but scope behind does nothing
for({int i=0; j=0;} i<10; ++i, {++i; ++j;} ){}
// endless loop
for({int i=0; j=0;} i<10; {++i; ++j;} ){}
```
Not sure if bug or feature but it is inconsistent for me and
thus a reason to avoid it.
That's because `{++i; ++j;}` in an expression context is
shorthand syntax for `delegate void () {++i; ++j;}`.
If you look at the [grammar for the `for` statement][1], you'll
see that the "initialize" part allows a *statement*, but the
"test" and "increment" parts only allow *expressions*.
[1]: https://dlang.org/spec/statement.html#ForStatement
Re: Wouldn't the compiler be smart with this shadowing variable?
On Saturday, 11 December 2021 at 15:15:06 UTC, Matheus wrote:
I'm just a bit intrigued by your last sentence. Is there
anything evil this may result or anything that I should be
aware of?
Besides it looks like an error, you may think that it just
introduces a scope which can be referenced by the for-loop but
this only works in the initialization section. See what happens
if you want to do more steps at iteration for this fancy looking
syntax:
```d
// iteration works, but scope behind does nothing
for({int i=0; j=0;} i<10; ++i, {++i; ++j;} ){}
// endless loop
for({int i=0; j=0;} i<10; {++i; ++j;} ){}
```
Not sure if bug or feature but it is inconsistent for me and thus
a reason to avoid it.
Re: Wouldn't the compiler be smart with this shadowing variable?
On Saturday, 11 December 2021 at 01:02:36 UTC, frame wrote:
...
You probably want this:
```d
int j;
for({int i=0; j=0;} i<10; ++i){}
```
Beware, this syntax comes directly from hell
Well this works! :)
I'm just a bit intrigued by your last sentence. Is there anything
evil this may result or anything that I should be aware of?
Matheus.
Re: Wouldn't the compiler be smart with this shadowing variable?
On Friday, 10 December 2021 at 21:55:17 UTC, Siarhei Siamashka wrote: ... 2. reuse the existing "j" variable. Yes. But only one of them is a correct description of what actually happens when the compiler processes this code. So it's a good thing that the compiler is smart enough to reject ambiguous code and prevent humans from making mistakes. Hmm I see your point. And I just thought in cases like this the reuse should be the way, but I can see that this is a small snippet and in a big code this may hurt someone. Matheus.
Re: Wouldn't the compiler be smart with this shadowing variable?
On Friday, 10 December 2021 at 13:35:37 UTC, Matheus wrote:
I mean this is a bit weird, imagine I have different "for
loops" and in this situation I'll need to do this:
j=0;
for(int i=0;i<10;++i){}
Otherwise:
for(i=0,j=0;i<10;++i){}
This works, but now "i" variable will be out of the "for loop"
scope.
Matheus.
You probably want this:
```d
int j;
for({int i=0; j=0;} i<10; ++i){}
```
Beware, this syntax comes directly from hell
Re: Wouldn't the compiler be smart with this shadowing variable?
On Friday, 10 December 2021 at 13:35:37 UTC, Matheus wrote:
Hi,
Wouldn't the compiler be smart with this shadowing variable,
example:
void main(){
int j;
for(int i=0,j=0;i<10;++i){}
return;
}
onlineapp.d(3): Error: variable `j` is shadowing variable
`onlineapp.main.j`
So in the "for loop" shouldn't "i" be declared and "j" just be
assigned to 0?
Intuitively, there are two possible interpretations here for
inexperienced humans (and you seem to be favoring the latter):
1. declare a new "j" variable to be visible only inside of the
loop.
2. reuse the existing "j" variable.
But only one of them is a correct description of what actually
happens when the compiler processes this code. So it's a good
thing that the compiler is smart enough to reject ambiguous code
and prevent humans from making mistakes.
Wouldn't the compiler be smart with this shadowing variable?
Hi,
Wouldn't the compiler be smart with this shadowing variable,
example:
void main(){
int j;
for(int i=0,j=0;i<10;++i){}
return;
}
onlineapp.d(3): Error: variable `j` is shadowing variable
`onlineapp.main.j`
So in the "for loop" shouldn't "i" be declared and "j" just be
assigned to 0?
I mean this is a bit weird, imagine I have different "for loops"
and in this situation I'll need to do this:
j=0;
for(int i=0;i<10;++i){}
Otherwise:
for(i=0,j=0;i<10;++i){}
This works, but now "i" variable will be out of the "for loop"
scope.
Matheus.
