> The right way to define this is to say that objects have a value representation consisting
of a fixed subset of the bits of their object representation, and that the value of an object
is the sequence of bits in the value representation.
Not quite, while the value representation of an trivially copyable type will appear in the object representation, for an object of non-trivially copyable type, the value is a user established thing: such as `std::string`, since it has a pointer to external data.
Not not quite. Pick your own words if you want, but we should have one word
for the contents of the value representation and another for the "user-established
thing". I like "same" for the former and "equal" for the latter, so two std::string
objects are the same if they point to the same external data (makes more sense
for string views), and are equal if they point to identical sequences of characters.
What is the value in having a word for "has the same bits", when almost nothing in the language cares about having the same bits?
If we do have a word for it, should it use a short and generic word like "same", or something more specific? (ie "bitwise-equal"?)
This conversation started with a wording question/suggestion that revolves around the word "value".
I asked:
> Are you then going to continue, and define what value is?
I should have probably not just asked a question in such a "Socratic" manner. (ie Hoping the question would reveal larger insights.)
I should probably have said:
About a year ago, I tried to understand what "value" means in the standard. The word occurs over 1000 times. I read them *all*, multiple times.
- As you can imagine, it wasn't entirely clear, and possibly inconsistent.
- The library usage is less clear than core. Library tends to mean "==". Or maybe "consistent with ==".
- Core tends to mean "the number that is being represented". int x = 1 means x has the mathematical value of 1. And double y = 1.0 has the same value. We don't define what 1 is, we rely on math for that. (And it is very tricky, see Gottlob Frege's "The Foundations of Arithmetic" (1884) for a great, but failed, attempt at defining 1.) See also Stepanov's EoP for some fundamental definitions.
My conclusion would be that it would be really hard to define "value" in the standard, in a useful way that is consistent with most of the current uses of "value".
At the same time, the beauty of C++ is that we can raise our thinking to the level of "value", and implement our own classes with their own meaning of value. As long as the class's definition of value is sensible, everything falls into place - the STL works as expect, as does the core language, etc.
I don't think the definition of value has much, if anything, to do with bits.
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