## digitalmars.D.learn - Assignment in ternary condition operator

• JN (8/8) Aug 07 2018 int a, b;
• Steven Schveighoffer (16/28) Aug 07 2018 But operator precedence says that this is really:
• JN (5/23) Aug 07 2018 Ahhhh. I didn't think of that. Hmm, I guess a warning here would
```int a, b;

if (a = 3) { }   <- not allowed: Error: assignment cannot be used
as a condition, perhaps == was meant?

b = a = 3 ? 4 : 5   <- allowed

I believe the second case should be disallowed also. It seems
illogical, that the first one isn't allowed, but the second one
is, when the second one is also 'assignment used as condition'.
Is there a valid usecase for such assignment?
```
Aug 07 2018
```On 8/7/18 3:18 PM, JN wrote:
int a, b;

if (a = 3) { }   <- not allowed: Error: assignment cannot be used as a
condition, perhaps == was meant?

b = a = 3 ? 4 : 5   <- allowed

I believe the second case should be disallowed also. It seems illogical,
that the first one isn't allowed, but the second one is, when the second
one is also 'assignment used as condition'. Is there a valid usecase for
such assignment?

But operator precedence says that this is really:

b = (a = (3 ? 4 : 5))

It's a different thing than the if statement. In the if statement, it's
the *assignment* that is now the condition. Here, it is not an
assignment that is the condition, but `3`. There is no common error that
requires preventing assignment from the result of an assignment.

I realize that what you seeing is a typo from:

b = a == 3 ? 4 : 5

but the problem is that you are relying on precedence incorrectly here.
If you type:

b = (a = 3) ? 4 : 5

Then you get the error. D can't solve all the problems. Best thing to do
is to use parentheses to clarify what you want for your condition rather
than rely on default order of operations.

-Steve
```
Aug 07 2018
```On Tuesday, 7 August 2018 at 19:58:40 UTC, Steven Schveighoffer
wrote:
On 8/7/18 3:18 PM, JN wrote:
[...]

But operator precedence says that this is really:

b = (a = (3 ? 4 : 5))

It's a different thing than the if statement. In the if
statement, it's the *assignment* that is now the condition.
Here, it is not an assignment that is the condition, but `3`.
There is no common error that requires preventing assignment
from the result of an assignment.

I realize that what you seeing is a typo from:

b = a == 3 ? 4 : 5

but the problem is that you are relying on precedence
incorrectly here. If you type:

b = (a = 3) ? 4 : 5

Then you get the error. D can't solve all the problems. Best
thing to do is to use parentheses to clarify what you want for
your condition rather than rely on default order of operations.

-Steve

Ahhhh. I didn't think of that. Hmm, I guess a warning here would
be nice then, or perhaps DScanner could mark such cases as
suspicious :)
```
Aug 07 2018