is vs ==

[Steven Schveighoffer]

On Saturday, 30 August 2025 at 22:15:26 UTC, Brother Bill wrote:
> For the modern D developer, which is the more preferred choice, 
> to use 'is' or '=='?

`is` will do a direct bitwise comparison of the two sides, and 
cannot be hooked with an operator overload. This tests for 
*identity* (are the two sides the same instance).

`==` will use a type-specific comparison controlled by either the 
lhs type or the rhs type. This tests for *logical equality*.

> Do the Style Guidelines or other authorities prefer one to the 
> other for modern D coding?
>
> Or is either equally satisfactory?

For value types that do not hook logical equality, `is` and `==` 
can be the same operation. There are some exceptions, for example 
floating-point numbers.

`is` is generally preferred for pointer or reference comparisons.

-Steve