Comment by zzo38computer
4 days ago
I think it would be better to not use Unicode (so that you can use any character set), and to use "0o" instead of "0" prefix for octal numbers. Also, EDN seems to lack a proper format for binary data.
I think ASN.1 (and ASN.1X which is I added a few additional types such as key/value list and TRON string) is better. (I also made up a text-based ASN.1 format called TER which is intended to be converted to the binary DER format. It is also intended that extensions and subsets of TER can be made for specific applications if needed.) (I also wrote a DER decoder/encoder library in C, and programs that use that library, to convert TER to DER and to convert JSON to DER.)
ASN.1 (and ASN.1X) has many similar types than EDN, and a comparison can be made:
- Null (called "nil" in EDN) and booleans are available in ASN.1.
- Strings in ASN.1 are fortunately not limited to Unicode; you can also use ISO 2022, as well as octet strings and bit strings. However, there is no "single character" type.
- ASN.1 does have a Enumerated type, although the enumeration is made as numbers rather than as names. The EDN "keywords" type seems to be intended for enumerations.
- The integer and floating point types in ASN.1 are already arbitrary precision. If a reader requires a limited precision (e.g. 64-bits), it is easy to detect if it is out of range and result in an error condition.
- ASN.1 does not have a separate "list" and "vector" type, but does have a "set" type and a "sequence" type. A key/value list ("map") type is a nonstandard type in ASN.1X, but standard ASN.1 does not have a key/value list type.
- ASN.1 does have tagging, although its working is difference from EDN. ASN.1 does already have a date/time type though, so this extension is not needed. Extensions are possible by application types and private types, as well as by other methods such as External, Embedded PDV, and the nonstandard
- The rational number type (in edn.c but the main EDN specification does not seems to mention it), is not a standard type in ASN.1 but ASN.1X does have such a type.
(Some people complain that ASN.1 is complicated; this is not wrong, but you will only need to implement the parts that you will use (which is simpler when using DER rather than BER; I think BER is not very good and DER is much better), which ends up making it simpler while also capable of doing the things that would be desirable.)
(But, EDN does solve some of the problems with JSON, such as comments and a proper integer type.)
> EDN seems to lack a proper format for binary data
The best part of EDN that it is extendable :)
#binary/base64 "SGVsbG8sIHp6bzM4Y29tcHV0ZXIhIEhvdyBhcmUgeW91IGRvaW5nPw=="
This is a tagged literal that can be read by provided (if provided) custom reader during reading of the document. The result could be any type you want.
OK, this is possible, but it seems the type that ought to be a built-in type.
Also, if there is not a binary file format for the data then you will need to always convert to/from base64 when working with this file whether or not you should need to.
Furthermore, this does not work very well when you want to deal with character sets rather than binary data, since (as far as I can tell from the specification) the input will still need to be UTF-8 and follow the EDN syntax of an existing type.
From what I can understand from the specification, the EDN decoder will still need to run and cannot be streamed if the official specification is used (which can make it inefficient), although it would probably be possible to make an implementation that can do this with streaming instead (but I don't know if the existing one does).
So, the extensibility is still restricted. (In my opinion, ASN.1 (and ASN.1X) does it better.)
> From what I can understand from the specification, the EDN decoder will still need to run and cannot be streamed if the official specification is used
Sorry, you understand it wrong
There is no enclosing element at the top level. Thus edn is suitable for streaming and interactive applications.
> but I don't know if the existing one does
This implementation does not do streaming for now, but it understands a concept of "reading one complete" element from buffer. The only missing part is buffer managment.
> So, the extensibility is still restricted.
Could you explain how it is restricted if you are allowed to run whatever you want during reading of edn document? You can even do IO, no restrictions at all!
Consider this:
#init/postgres {:db-spec {:host "..." :port 54321 ,,,} :specs {:user ,,,}} [#user/id 1 #user/id 2 #user/id 3]
This allows you to have a program that can lookup postgres database during reading of a document validating every returned object using provided spec (conforming the value)
> In my opinion, ASN.1 (and ASN.1X) does it better.
Please show how it does better. I'm very curious
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