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@ -298,73 +298,122 @@ connections to other data languages can also be made.
For now, we limit our attention to an easily-parsed, easily-produced
machine-readable syntax.
Every `Value` is represented as one or more bytes describing first its
kind and its length, and then its specific contents.
A `Repr` is an encoding, or representation, of a specific `Value`.
Each `Repr` comprises one or more bytes describing first the kind of
represented `Value` and the length of the representation, and then the
encoded details of the `Value` itself.
For a value `v`, we write `[[v]]` for the encoding of v.
For a value `v`, we write `[[v]]` for the `Repr` of v.
The following figure summarises the definitions below:
tt nn mmmm varint(m) contents
-------------------------------
00 00 mmmm ... application-specific Record
00 01 mmmm ... application-specific Record
00 10 mmmm ... application-specific Record
00 11 mmmm ... Record
00 00 0000 False
00 00 0001 True
00 00 0010 Float, 32 bits big-endian binary
00 00 0011 Double, 64 bits big-endian binary
00 00 x1xx RESERVED
00 00 1xxx RESERVED
00 01 xxxx RESERVED
00 10 ttnn Start Stream <tt,nn>
When tt = 00 --> error
01 --> each chunk is a <tt,nn> piece
1x --> each chunk is a single encoded Value
00 11 ttnn End Stream <tt,nn> (must match preceding Start Stream)
01 00 mmmm ... Sequence
01 01 mmmm ... Set
01 10 mmmm ... Dictionary
01 00 mmmm ... SignedInteger, big-endian binary
01 01 mmmm ... String, UTF-8 binary
01 10 mmmm ... Bytes
01 11 mmmm ... Symbol, UTF-8 binary
10 00 mmmm ... SignedInteger, big-endian binary
10 01 mmmm ... String, UTF-8 binary
10 10 mmmm ... Bytes
10 11 mmmm ... Symbol, UTF-8 binary
10 00 mmmm ... application-specific Record
10 01 mmmm ... application-specific Record
10 10 mmmm ... application-specific Record
10 11 mmmm ... Record
11 00 0000 False
11 00 0001 True
11 00 0010 Float, 32 bits big-endian binary
11 00 0011 Double, 64 bits big-endian binary
11 00 mmmm ... Sequence
11 01 mmmm ... Set
11 10 mmmm ... Dictionary
11 11 xxxx RESERVED
If mmmm = 1111, varint(m) is present; otherwise, m is the length
#### Type and Length representation
A `Value`'s type and length is represented by use of a function
`header(t,n,m)` that yields a sequence of bytes when `t`, `n` and `m`
are appropriate non-negative integers.
Each `Repr` takes one of three possible forms:
header(t,n,m) = leadbyte(t,n,m) when m < 15
or leadbyte(t,n,15) ++ varint(m) otherwise
- (A) a fixed-length form, used for simple values such as `Boolean`s
or `Float`s.
The lead byte in a `Value`'s representation is constructed by a function
- (B) a variable-length form with length specified up-front, used for
almost all `Record`s as well as for most `Sequence`s and `String`s,
when their sizes are known at the time serialization begins.
- (C) a variable-length streaming form with unknown or unpredictable
length, used only seldom for `Record`s, since the number of fields
in a `Record` is usually statically known, but sometimes used for
`Sequence`s, `String`s etc., such as in cases when serialization
begins before the number of elements or bytes in the corresponding
`Value` is known.
Applications may choose between formats (B) and (C) depending on their
needs at serialization time.
Every `Repr`, however, starts with a *lead byte* describing the
remainder of the representation.
##### The lead byte
The lead byte is constructed by a function `leadbyte`:
leadbyte(t,n,m) = [t*64 + n*16 + m]
Both `t` and `n` are two-bit unsigned numbers; `m` is a four-bit
unsigned number.
The lead byte describes the rest of the representation as
follows:[^some-encodings-unused]
leadbyte(0,-,-) represents a Record
leadbyte(1,-,-) represents a Sequence, Set or Dictionary
leadbyte(2,-,-) represents an Atom with variable-length binary representation
leadbyte(3,0,-) represents an Atom with fixed-length binary representation
[^some-encodings-unused]: Some encodings are unused. All such
encodings are reserved for future versions of this specification.
Variable-length representations use the value of `m` to encode their
lengths:
- `leadbyte(0,0,-)` (format A) represents an Atom with fixed-length binary representation.
- `leadbyte(0,1,-)` (format A) is RESERVED.
- `leadbyte(0,2,-)` (format C) is a Stream Start byte.
- `leadbyte(0,3,-)` (format C) is a Stream End byte.
- `leadbyte(1,-,-)` (format B) represents an Atom with variable-length binary representation.
- `leadbyte(2,-,-)` (format B) represents a Record.
- `leadbyte(3,-,-)` (format B) represents a Sequence, Set or Dictionary.
- Lengths between 0 and 14 are represented using `leadbyte` with `m`
values 0 through 14.
- Lengths of 15 or greater are represented by `m` value 15, and
additional "length bytes" describing the length then follow the
lead byte.
##### Encoding data of fixed length (format A)
These additional length bytes are formatted as
[base 128 varints][varint]. Quoting the
[Google Protocol Buffers][varint] definition,
Each specific type of data defines its own rules for this format.
##### Encoding data of known length (format B)
A `Repr` where the length of the `Value` to be encoded is variable but
known uses the value of `m` in `leadbyte` to encode its length. The
length counts *bytes* for atomic `Value`s, but counts *contained
values* for compound `Value`s.
- A length `l` between 0 and 14 is represented using `leadbyte` with
`m=l`.
- A length of 15 or greater is represented by `m=15` and additional
bytes describing the length following the lead byte.
The function `header(t,n,m)` yields an appropriate sequence of bytes
describing a `Repr`'s type and length when `t`, `n` and `m` are
appropriate non-negative integers:
header(t,n,m) = leadbyte(t,n,m) when m < 15
or leadbyte(t,n,15) ++ varint(m) otherwise
The additional length bytes are formatted as
[base 128 varints][varint]. We write `varint(m)` for the
varint-encoding of `m`. Quoting the [Google Protocol Buffers][varint]
definition,
> Each byte in a varint, except the last byte, has the most
> significant bit (msb) set – this indicates that there are further
@ -378,43 +427,93 @@ These additional length bytes are formatted as
- 300 (binary, grouped into 7-bit chunks, `10 0101100`) varint-encodes to the two bytes 172 and 2.
- 1000000000 (binary `11 1011100 1101011 0010100 0000000`) varint-encodes to bytes 128, 148, 235, 220, and 3.
We write `varint(m)` for the varint-encoding of `m`.
##### Streaming data of unknown length (format C)
A `Repr` where the length of the `Value` to be encoded is variable and
not known at the time serialization of the `Value` starts is encoded
by a single Stream Start byte, followed by zero or more *chunks*,
followed by a matching Stream End byte:
startbyte(t,n) = leadbyte(0,2, t*4 + n)
endbyte(t,n) = leadbyte(0,3, t*4 + n)
For a `Repr` of a `Value` containing binary data, each chunk is to be
a format B `Repr` of the same type as the overall `Repr`.
For a `Repr` of a `Value` containing other `Value`s, each chunk is to
be a single `Repr`.
#### Records
[[ (L F_1 ... F_m) ]] = header(0,3,m+1) ++ [[L]] ++ [[F_1]] ++ ... ++ [[F_m]]
Format B (known length):
[[ (L F_1 ... F_m) ]] = header(2,3,m+1) ++ [[L]] ++ [[F_1]] ++ ... ++ [[F_m]]
For `m` fields, `m+1` is supplied to `header`, to account for the
encoding of the record label.
Format C (streaming):
[[ (L F_1 ... F_m) ]]
= startbyte(2,3) ++ [[L]] ++ [[F_1]] ++ ... ++ [[F_m]] ++ endbyte(2,3)
Applications *SHOULD* prefer the known-length format for encoding
`Record`s.
##### Application-specific short form for labels
Any given protocol using Preserves may additionally define an
interpretation for `n ∈ {0,1,2}`, mapping each *short form label
number* `n` to a specific record label. When encoding `m` fields with
short form label number `n`, the header is `header(0,n,m)` (rather
than `m+1`) since the label is implicit.
short form label number `n`, format B becomes
header(2,n,m) ++ [[F_1]] ++ ... ++ [[F_m]]
and format C becomes
startbyte(2,n) ++ [[F_1]] ++ ... ++ [[F_m]] ++ endbyte(2,n)
**Examples.** For example, a protocol may choose to map records
labelled `void` to `n=0`, making
[[(void)]] = header(0,0,0) = [0x00]
[[(void)]] = header(2,0,0) = [0x80]
or it may map records labelled `person` to short form label number 1,
making
[[(person "Dr" "Elizabeth" "Blackwell")]]
= header(0,1,3) ++ [["Dr"]] ++ [["Elizabeth"]] ++ [["Blackwell"]]`
= [0x13] ++ [["Dr"]] ++ [["Elizabeth"]] ++ [["Blackwell"]]`
= header(2,1,3) ++ [["Dr"]] ++ [["Elizabeth"]] ++ [["Blackwell"]]
= [0x93] ++ [["Dr"]] ++ [["Elizabeth"]] ++ [["Blackwell"]]
for format B, or
= startbyte(2,1) ++ [["Dr"]] ++ [["Elizabeth"]] ++ [["Blackwell"]] ++ endbyte(2,1)
= [0x29] ++ [["Dr"]] ++ [["Elizabeth"]] ++ [["Blackwell"]] ++ [0x39]
for format C.
#### Sequences, Sets and Dictionaries
[[ [X_1 ... X_m] ]] = header(1,0,m) ++ [[X_1]] ++ ... ++ [[X_m]]
Format B (known length):
[[ #set{X_1 ... X_m} ]] = header(1,1,m) ++ [[X_1]] ++ ... ++ [[X_m]]
[[ [X_1 ... X_m] ]] = header(3,0,m) ++ [[X_1]] ++ ... ++ [[X_m]]
[[ #set{X_1 ... X_m} ]] = header(3,1,m) ++ [[X_1]] ++ ... ++ [[X_m]]
[[ #dict{K_1:V_1 ... K_m:V_m} ]]
= header(1,2,m) ++ [[K_1]] ++ [[V_1]] ++ ... ++ [[K_m]] ++ [[V_m]]
= header(3,2,m) ++ [[K_1]] ++ [[V_1]] ++ ... ++ [[K_m]] ++ [[V_m]]
Format C (streaming):
[[ [X_1 ... X_m] ]] = startbyte(3,0) ++ [[X_1]] ++ ... ++ [[X_m]] ++ endbyte(3,0)
[[ #set{X_1 ... X_m} ]] = startbyte(3,1) ++ [[X_1]] ++ ... ++ [[X_m]] ++ endbyte(3,1)
[[ #dict{K_1:V_1 ... K_m:V_m} ]]
= startbyte(3,2) ++ [[K_1]] ++ [[V_1]] ++ ... ++ [[K_m]] ++ [[V_m]] ++ endbyte(3,2)
Applications may use whichever format suits their needs on a
case-by-case basis.
There is *no* ordering requirement on the `X_i` elements or
`K_i`/`V_i` pairs.[^no-sorting-rationale] They may appear in any
@ -432,19 +531,23 @@ order.
(b) sorting keys or elements makes no sense in streaming
serialization formats.
Note that `n=3` is unused and reserved.
Note that `header(3,3,m)` and `startbyte(3,3)`/`endbyte(3,3)` is unused and reserved.
#### Variable-length Atoms
##### SignedInteger
[[ x ]] when x ∈ SignedInteger = header(2,0,m) ++ intbytes(x)
Format B (known length):
[[ x ]] when x ∈ SignedInteger = header(1,0,m) ++ intbytes(x)
where m = |intbytes(x)|
and intbytes(x) = a big-endian two's-complement representation
of the signed integer x, taking exactly as
many whole bytes as needed to unambiguously
identify the value
Format C *MUST NOT* be used for `SignedInteger`s.
The value 0 needs zero bytes to identify the value, so `intbytes(0)`
is the empty byte string. Non-zero values need at least one byte; the
most-significant bit in the first byte in `intbytes(x)` for `x≠0` is
@ -452,55 +555,78 @@ the sign bit.
For example,
[[ -257 ]] = [0x82, 0xFE, 0xFF]
[[ -256 ]] = [0x82, 0xFF, 0x00]
[[ -255 ]] = [0x82, 0xFF, 0x01]
[[ -254 ]] = [0x82, 0xFF, 0x02]
[[ -129 ]] = [0x82, 0xFF, 0x7F]
[[ -128 ]] = [0x81, 0x80]
[[ -127 ]] = [0x81, 0x81]
[[ -2 ]] = [0x81, 0xFE]
[[ -1 ]] = [0x81, 0xFF]
[[ 0 ]] = [0x80]
[[ 1 ]] = [0x81, 0x01]
[[ 127 ]] = [0x81, 0x7F]
[[ 128 ]] = [0x82, 0x00, 0x80]
[[ 255 ]] = [0x82, 0x00, 0xFF]
[[ 256 ]] = [0x82, 0x01, 0x00]
[[ 32767 ]] = [0x82, 0x7F, 0xFF]
[[ 32768 ]] = [0x83, 0x00, 0x80, 0x00]
[[ 65535 ]] = [0x83, 0x00, 0xFF, 0xFF]
[[ 65536 ]] = [0x83, 0x01, 0x00, 0x00]
[[ 131072 ]] = [0x83, 0x02, 0x00, 0x00]
[[ -257 ]] = [0x42, 0xFE, 0xFF]
[[ -256 ]] = [0x42, 0xFF, 0x00]
[[ -255 ]] = [0x42, 0xFF, 0x01]
[[ -254 ]] = [0x42, 0xFF, 0x02]
[[ -129 ]] = [0x42, 0xFF, 0x7F]
[[ -128 ]] = [0x41, 0x80]
[[ -127 ]] = [0x41, 0x81]
[[ -2 ]] = [0x41, 0xFE]
[[ -1 ]] = [0x41, 0xFF]
[[ 0 ]] = [0x40]
[[ 1 ]] = [0x41, 0x01]
[[ 127 ]] = [0x41, 0x7F]
[[ 128 ]] = [0x42, 0x00, 0x80]
[[ 255 ]] = [0x42, 0x00, 0xFF]
[[ 256 ]] = [0x42, 0x01, 0x00]
[[ 32767 ]] = [0x42, 0x7F, 0xFF]
[[ 32768 ]] = [0x43, 0x00, 0x80, 0x00]
[[ 65535 ]] = [0x43, 0x00, 0xFF, 0xFF]
[[ 65536 ]] = [0x43, 0x01, 0x00, 0x00]
[[ 131072 ]] = [0x43, 0x02, 0x00, 0x00]
##### String
[[ S ]] when S ∈ String = header(2,1,m) ++ utf8(S)
Format B (known length):
[[ S ]] when S ∈ String = header(1,1,m) ++ utf8(S)
where m = |utf8(x)|
and utf8(x) = the UTF-8 encoding of S
To stream a `String`, emit `startbyte(1,1)` and then a sequence of
zero or more format B `String` chunks, followed by `endbyte(1,1)`.
While the overall content of a streamed `String` must be valid UTF-8,
individual chunks do not have to conform to UTF-8.
##### ByteString
[[ B ]] when B ∈ ByteString = header(2,2,m) ++ B
Format B (known length):
[[ B ]] when B ∈ ByteString = header(1,2,m) ++ B
where m = |B|
To stream a `ByteString`, emit `startbyte(1,2)` and then a sequence of
zero or more format B `ByteString` chunks, followed by `endbyte(1,2)`.
##### Symbol
[[ S ]] when S ∈ Symbol = header(2,2,m) ++ utf8(S)
Format B (known length):
[[ S ]] when S ∈ Symbol = header(1,3,m) ++ utf8(S)
where m = |utf8(x)|
and utf8(x) = the UTF-8 encoding of S
To stream a `Symbol`, emit `startbyte(1,3)` and then a sequence of
zero or more format B `Symbol` chunks, followed by `endbyte(1,3)`.
#### Fixed-length Atoms
Fixed-length atoms all use format A, and do not have a length
representation. They repurpose the bits that format B `Repr`s use to
specify lengths. Applications *MUST NOT* use format C with
`startbyte(0,n)` or `endbyte(0,n)` for any `n`.
##### Booleans
[[ #f ]] = header(3,0,0) = [0xC0]
[[ #t ]] = header(3,0,1) = [0xC1]
[[ #f ]] = header(0,0,0) = [0x00]
[[ #t ]] = header(0,0,1) = [0x01]
##### Floats and Doubles
[[ F ]] when F ∈ Float = header(3,0,2) ++ binary32(F)
[[ D ]] when D ∈ Double = header(3,0,3) ++ binary64(D)
[[ F ]] when F ∈ Float = header(0,0,2) ++ binary32(F)
[[ D ]] when D ∈ Double = header(0,0,3) ++ binary64(D)
where binary32(F) and binary64(D) are big-endian 4- and 8-byte
IEEE 754 binary representations
@ -515,21 +641,25 @@ short form label number 0 to label `discard`, 1 to `capture`, and 2 to
| Value | Encoded hexadecimal byte sequence |
|--------------------------------------------------------------------|----------------------------------------------------|
| `(capture (discard))` | 11 00 |
| `(observe (speak (discard) (capture (discard))))` | 21 33 B5 73 70 65 61 6B 00 11 00 |
| `[1 2 3 4]` | 44 81 01 81 02 81 03 81 04 |
| `[-2 -1 0 1]` | 54 81 FE 81 FF 80 81 01 |
| `["hello" there #"world" [] #set{} #t #f]` | 47 95 68 65 6C 6C 6F A5 74 68 65 72 65 40 50 C1 C0 |
| `-257` | 82 FE FF |
| `-1` | 81 FF |
| `0` | 80 |
| `1` | 81 01 |
| `255` | 82 00 FF |
| `1f` | C2 3F 80 00 00 |
| `1d` | C3 3F F0 00 00 00 00 00 00 |
| `-1.202e300d` | C3 FE 3C B7 B7 59 BF 04 26 |
| `(capture (discard))` | 91 80 |
| `(observe (speak (discard) (capture (discard))))` | A1 B3 75 73 70 65 61 6B 80 91 80 |
| `[1 2 3 4]` (format B) | C4 41 01 41 02 41 03 41 04 |
| `[1 2 3 4]` (format C) | 2C 41 01 41 02 41 03 41 04 3C |
| `[-2 -1 0 1]` | C4 41 FE 41 FF 40 41 01 |
| `"hello"` (format B) | 55 68 65 6C 6C 6F |
| `"hello"` (format C, 2 chunks) | 25 52 68 65 53 6C 6C 6F 35 |
| `"hello"` (format C, 5 chunks) | 25 52 68 65 52 6C 6C 50 50 51 6F 35 |
| `["hello" there #"world" [] #set{} #t #f]` | C7 55 68 65 6C 6C 6F 75 74 68 65 72 65 C0 D0 01 00 |
| `-257` | 42 FE FF |
| `-1` | 41 FF |
| `0` | 40 |
| `1` | 41 01 |
| `255` | 42 00 FF |
| `1f` | 02 3F 80 00 00 |
| `1d` | 03 3F F0 00 00 00 00 00 00 |
| `-1.202e300d` | 03 FE 3C B7 B7 59 BF 04 26 |
Finally, a larger example, using a non-`Symbol` label for a record.[^extensibility2] The `Value`
Finally, a larger example, using a non-`Symbol` label for a record.[^extensibility2] The `Record`
([titled person 2 thing 1]
101
@ -539,21 +669,21 @@ Finally, a larger example, using a non-`Symbol` label for a record.[^extensibili
encodes to
35 ;; Record, generic, 4+1
45 ;; Sequence, 5
B6 74 69 74 6C 65 64 ;; Symbol, "titled"
B6 70 65 72 73 6F 6E ;; Symbol, "person"
81 02 ;; SignedInteger, "2"
B5 74 68 69 6E 67 ;; Symbol, "thing"
81 01 ;; SignedInteger, "1"
81 65 ;; SignedInteger, "101"
99 42 6C 61 63 6B 77 65 6C 6C ;; String, "Blackwell"
34 ;; Record, generic, 3+1
B4 64 61 74 65 ;; Symbol, "date"
82 07 1D ;; SignedInteger, "1821"
81 02 ;; SignedInteger, "2"
81 03 ;; SignedInteger, "3"
92 44 72 ;; String, "Dr"
B5 ;; Record, generic, 4+1
C5 ;; Sequence, 5
76 74 69 74 6C 65 64 ;; Symbol, "titled"
76 70 65 72 73 6F 6E ;; Symbol, "person"
41 02 ;; SignedInteger, "2"
75 74 68 69 6E 67 ;; Symbol, "thing"
41 01 ;; SignedInteger, "1"
41 65 ;; SignedInteger, "101"
59 42 6C 61 63 6B 77 65 6C 6C ;; String, "Blackwell"
B4 ;; Record, generic, 3+1
74 64 61 74 65 ;; Symbol, "date"
42 07 1D ;; SignedInteger, "1821"
41 02 ;; SignedInteger, "2"
41 03 ;; SignedInteger, "3"
52 44 72 ;; String, "Dr"
[^extensibility2]: It happens to line up with Racket's
representation of a record label for an inheritance hierarchy
@ -608,15 +738,15 @@ pair.
**Examples.**
| `(mime application/octet-stream #"abcde")` | 33 B4 6D 69 6D 65 BF 18 61 70 70 6C 69 63 61 74 69 6F 6E 2F 6F 63 74 65 74 2D 73 74 72 65 61 6D A5 61 62 63 64 65 |
| `(mime text/plain "ABC")` | 33 B4 6D 69 6D 65 BA 74 65 78 74 2F 70 6C 61 69 6E 93 41 42 43 |
| `(mime application/xml "<xhtml/>")` | 33 B4 6D 69 6D 65 BF 0F 61 70 70 6C 69 63 61 74 69 6F 6E 2F 78 6D 6C 98 3C 78 68 74 6D 6C 2F 3E |
| `(mime text/csv "123,234,345")` | 33 B4 6D 69 6D 65 B8 74 65 78 74 2F 63 73 76 9B 31 32 33 2C 32 33 34 2C 33 34 35 |
| `(mime application/octet-stream #"abcde")` | B3 74 6D 69 6D 65 7F 18 61 70 70 6C 69 63 61 74 69 6F 6E 2F 6F 63 74 65 74 2D 73 74 72 65 61 6D 65 61 62 63 64 65 |
| `(mime text/plain #"ABC")` | B3 74 6D 69 6D 65 7A 74 65 78 74 2F 70 6C 61 69 6E 63 41 42 43 |
| `(mime application/xml #"<xhtml/>")` | B3 74 6D 69 6D 65 7F 0F 61 70 70 6C 69 63 61 74 69 6F 6E 2F 78 6D 6C 68 3C 78 68 74 6D 6C 2F 3E |
| `(mime text/csv #"123,234,345")` | B3 74 6D 69 6D 65 78 74 65 78 74 2F 63 73 76 6B 31 32 33 2C 32 33 34 2C 33 34 35 |
Applications making heavy use of `mime` records may choose to use a
short form label number for the record type. For example, if short
form label number 1 were chosen, the second example above, `(mime
text/plain "ABC")`, would be encoded with "12" in place of "33 B4 6D
text/plain "ABC")`, would be encoded with "92" in place of "B3 74 6D
69 6D 65".
### Text
@ -746,26 +876,29 @@ should both be identities.
## Appendix. Table of lead byte values
0x - short form Record label index 0
1x - short form Record label index 1
2x - short form Record label index 2
3x - Record
4x - Sequence
5x - Set
6x - Dictionary
(7x) RESERVED
8x - SignedInteger
9x - String
Ax - Bytes
Bx - Symbol
C0 - False
C1 - True
C2 - Float
C3 - Double
(Cx) RESERVED C4-CF
(Dx) RESERVED
(Ex) RESERVED
(Fx) RESERVED
00 - False
01 - True
02 - Float
03 - Double
(0x) RESERVED 04-0F
(1x) RESERVED 10-1F
2x - Start Stream
3x - End Stream
4x - SignedInteger
5x - String
6x - Bytes
7x - Symbol
8x - short form Record label index 0
9x - short form Record label index 1
Ax - short form Record label index 2
Bx - Record
Cx - Sequence
Dx - Set
Ex - Dictionary
(Fx) RESERVED F0-FF
## Appendix. Why not Just Use JSON?
@ -942,15 +1075,6 @@ Q. Should I map to SPKI SEXP or is that nonsense / for later?[^why-not-spki-sexp
other kind of structure, and the "hint" itself can only be a
binary blob.
Q. Should `MIMEData` be a special syntax for `Record`s with a single
`ByteString` field?
A. Not even. It should probably just be moved to the "conventions"
section. Compare:
D5 BA text/plain hello -- using special MIMEData encoding
32 BA text/plain A5 hello -- using bog standard type-labelled Record
Q. Should `Symbol` be a special syntax for a `Record` with a `Symbol`
label (recursive!?) and a single `String` field?
@ -970,16 +1094,6 @@ Q. Are the language mappings reasonable? How about one for Python?
---
Streaming: needed for variable-sized structures. Tricky to design
syntax for this that isn't gratuitously warty. End byte value.
SIGH. Streaming for text/bytes too I SUPPOSE. Chunks, like CBOR
Literal small integers: could be nice? Not absolutely necessary.
Maybe reorder: fixed-length atoms first, then variable-length atoms,
then fixed-length compounds, then variable-length compounds? Reason
being that then maybe can put the streaming forms of the
variable-length ones very last.
---