Preserves Quick Reference
Tony Garnock-Jones tonyg@leastfixedpoint.com
October 2023. Version 0.992.0.
These are non-normative “reference card” definitions. See also the normative semantics, text syntax specification, and machine-oriented syntax specification, and the experimental P-expressions definition.
Machine-Oriented Binary Syntax
For a value V, we write «V» for the binary encoding of V.
«@W V» |
= |
85 «W» «V» |
«#!V» |
= |
86 «V» |
| «V» |
= |
8704 binary32(V) |
if V ∈ Float |
| «V» |
= |
8708 binary64(V) |
if V ∈ Double |
| «V» |
= |
B0 varint(|intbytes(V)|) intbytes(V) |
if V ∈ SignedInteger |
| «V» |
= |
B1 varint(|utf8(V)|) utf8(V) |
if V ∈ String |
| «V» |
= |
B2 varint(|V|) V |
if V ∈ ByteString |
| «V» |
= |
B3 varint(|utf8(V)|) utf8(V) |
if V ∈ Symbol |
«<L F1 … Fm>» |
= |
B4 «L» «F1» … «Fm» 84 |
«[X1 … Xm]» |
= |
B5 «X1» … «Xm» 84 |
«#{E1 … Em}» |
= |
B6 «E1» … «Em» 84 |
«{K1:V1 … Km:Vm}» |
= |
B7 «K1» «V1» … «Km» «Vm» 84 |
| varint(n) |
= |
n |
if n < 128 |
| |
|
(n & 127) | 128 varint(n >> 7) |
if n ≥ 128 |
| intbytes(n) |
= |
the empty sequence if n = 0, otherwise signedBigEndian(n) |
| signedBigEndian(n) |
= |
n & 255 |
if −128 ≤ n ≤ 127 |
| |
|
signedBigEndian(n >> 8) n & 255 |
otherwise |
The functions binary32(F) and binary64(D) yield big-endian 4- and 8-byte
IEEE 754 binary representations of F and
D, respectively.
Human-Oriented Text Syntax
| Document |
:= |
Value ws |
| Value |
:= |
ws (Record | Collection | Embedded | Annotated | Atom) |
| Collection |
:= |
Sequence | Dictionary | Set |
| Record |
:= |
<Value+ ws> |
| Sequence |
:= |
[(commas Value)⋆ commas] |
| Set |
:= |
#{(commas Value)⋆ commas} |
| Dictionary |
:= |
{ (commas Value ws:Value)⋆ commas} |
| commas |
:= |
(ws ,)⋆ ws |
| Embedded |
:= |
#!Value |
| Annotated |
:= |
Annotation Value |
| Annotation |
:= |
@Value |# ((space | tab) linecomment) (cr | lf) |
| Atom |
:= |
Boolean | ByteString | String | QuotedSymbol | Symbol | Number |
| Boolean |
:= |
#t|#f |
| ByteString |
:= |
#"binchar⋆ "|#x" (ws hex hex)⋆ ws"|#[ (ws base64char)⋆ ws] |
| String |
:= |
" (« any unicode scalar value except \ or " » | escaped |\")⋆ " |
| QuotedSymbol |
:= |
| (« any unicode scalar value except \ or | » | escaped |\|)⋆ | |
| Symbol |
:= |
(A..Z|a..z|0..9| sympunct | symuchar)+ |
| Number |
:= |
Float | Double | SignedInteger |
| Float |
:= |
flt (f|F) |#xf" (ws hex hex)4 ws" |
| Double |
:= |
flt |#xd" (ws hex hex)8 ws" |
| SignedInteger |
:= |
int |
| escaped |
:= |
\\|\/|\b|\f|\n|\r|\t|\uhex hex hex hex |
| binescaped |
:= |
\\|\/|\b|\f|\n|\r|\t|\xhex hex |
| binchar |
:= |
« any unicode scalar value ≥32 and ≤126, except \ or " » | binescaped |\" |
| base64char |
:= |
A..Z|a..z|0..9|+|/|-|_|= |
| sympunct |
:= |
~|!|$|%|^|&|*|?|_|=|+|-|/|. |
| symuchar |
:= |
« any scalar value ≥128 whose Unicode category is Lu, Ll, Lt, Lm, Lo, Mn, Mc, Me, Nd, Nl, No, Pc, Pd, Po, Sc, Sm, Sk, So, or Co » |
| flt |
:= |
int ( frac exp | frac | exp ) |
| int |
:= |
(-|+) (0..9)+ |
| frac |
:= |
. (0..9)+ |
| exp |
:= |
(e|E) (-|+) (0..9)+ |
| hex |
:= |
A..F|a..f|0..9 |
| ws |
:= |
(space | tab | cr | lf)⋆ |
| delimiter |
:= |
ws | < | > | [ | ] | { | } | # | : | " | | | @ | ; | , |
| linecomment |
:= |
« any unicode scalar value except cr or lf »⋆ |
P-expression Syntax
The definitions of Atom, ws, and linecomment are as given in the Preserves text syntax.
| Document |
:= |
Expr⋆ Trailer ws |
| Expr |
:= |
ws (SimpleExpr | Punct) |
| SimpleExpr |
:= |
Compound | Embedded | Annotated | Atom |
| Compound |
:= |
Sequence | Record | Block | Group | Set |
| Punct |
:= |
, | ; | :+ |
| Sequence |
:= |
[ Expr⋆ Trailer ws ] |
| Record |
:= |
< Expr⋆ Trailer ws > |
| Block |
:= |
{ Expr⋆ Trailer ws } |
| Group |
:= |
( Expr⋆ Trailer ws ) |
| Set |
:= |
#{ Expr⋆ Trailer ws } |
| Trailer |
:= |
(ws Annotation)⋆ |
| Embedded |
:= |
#! SimpleExpr |
| Annotated |
:= |
Annotation SimpleExpr |
| Annotation |
:= |
@ SimpleExpr | # ((space | tab) linecomment) (cr | lf) |