pegasuscollins
As a user of both rust and and C++, I certainly wouldn't consider the the lack of default constructors in rust to be a good thing. Especially for std types like Vec it is really annoying to have to initialize it explicitly.
> The [dcl.init] section of the spec is about 16 pages long and there are about another dozen about how constructors work in the special member functions section.
That is a bad argument if you're comparing to a language that doesnt have a spec. Maybe a complete, exhaustive rust spec would be much longer than the C++ standard?
Agree that specifying the keys to be ordered >by unicode code points< instead of >lexicographically< would be less ambiguous though.
Are you speaking from personal experience? FWIW it doesn't match mine.
"Object members must be sorted by ascending lexicographic order of their keys."
To be pedantic: Not really. Assuming your example uses twos complement (what else would it use) and you meant "int32" instead of "uint32", negative zero and positive zero would still be the same encoded value. Also since you said "[u]int32", there is only one size the integer can be: 32 bit. So, in your example, the literal value zero has one and only one unique binary representation, which is "0x00000000"
The specification tells you all strings (keys) must be UTF8. There is only one lexicographic ordering of UTF8 strings (RFC3629, page 2). This should probably be explicitly mentioned in the linked specification though.
This generally is done for two major reasons: First of all, such an encoding is significantly easier and cheaper to parse than a base10+ascii (human-readable) encoding.
I encourage you to write a parser that reads a fixed, 32-bit binary number (1) and another parser that reads a JSON-formatted number string into an internal variable in a classic language like Java or C++. You will immediately see the big difference in complexity. Make sure your parser can also deal with a message that contains more than just one number, i.e. the parser should be able to tell at which byte index an encoded number begins and ends. Even if you're using a language or library where this is hidden from you (e.g. by using parseInt or std::stod) the same work still happens behind the scenes.
The other reason is that for most numbers and fixed/varint encoding schemes, the "binary" representation will be much more compact. Storing the number "1000000" in base10+ascii (human readable) takes at least eight bytes. Storing the same number in a fixed 32-bit integer encoding takes four bytes. Using a varint encoding scheme might allow you to get down to three bytes.
(1) Ignoring stuff like byte order and representation of negative numbers; this is usually fixed in the protocol/format specification.
EDIT: Also, using current exchange rates, the cost of living in one of the larger cities (Berlin, Munich, etc) in germany isnt that much lower compared to London anymore.