Syntax Specification

Conventions

Terminal symbols are written in $roman$ font.
Some special terminal symbols can be enclosed in $’single quotes’$ , or can be represented as a unicode literal like $U+2B7F$ .
Non-terminal syntactic symbols are written in $i t a l i c$ font.
Every non-terminal syntactic symbol names follow $P a s c a l e C a s e$ naming rule.
Non-terminal lexemes are written in $typewritter$ font.
Every non-terminal lexeme names follow $SCREAMING_SNAKE_CASE$ naming rule.
$EOF$ is a special lexeme denoting the end of input.
$ϵ$ denotes the empty string.
$A B$ means $A$ followed by $B$ .
$A ∣ B$ means either $A$ or $B$ .
$A^{n}$ is a sequence of $n$ iterations of $A$ .
$A^{*}$ is a sequence of zero or more iterations of $A$ , which is equivalent to $P ::= ϵ ∣ A P$ .
$A^{+}$ is a sequence of one or more iterations of $A$ , which is equivalent to $A A^{*}$ .
$A^{?}$ is an zero or one occurrence of $A$ , which is equivalent to $ϵ ∣ A$ .
$\sim A$ denotes any $C h a r$ except $A$ . ( $C h a r$ is defined here)
$A [B]$ denotes positive lookahead of $B$ , meaning $A$ followed by $B$ .
$A \sim [B]$ denotes negative lookahead of $B$ , meaning $A$ not followed by $B$ .
$⟨ A, B ⟩$ is a sequence of zero or more iterations of $A$ separated by $B$ , ending with optional $B$ , which is equivalent to $(A B)^{*} A^{?}$ .
Production rules are written in the form of $A ::= B$ .

Lexical Structure

Note that Dyn's lexical structure has context-free grammar.

Characters

\begin{matrix} C h a r & ::= & U+0000 ∣ \dots ∣ U+D7FF ∣ U+E000 ∣ \dots ∣ U+10FFFF \end{matrix}

Comments

\begin{array}{lcl} LINE_COMMENT & ::= & // \sim (U+000A ∣ EOF)^{*} \\ BLOCK_COMMENT & ::= & ’/*’ (\sim ’*’ ∣ ’*’ \sim [’/’] ∣ \sim ’/’ ∣ ’/’ \sim [’*’] ∣ BLOCK_COMMENT)^{*} ’*/’ \end{array}

White Spaces

\begin{array}{lcl} WHITESPACE & ::= & U+0009 \\ ∣ & U+000B \\ ∣ & U+000D \\ ∣ & U+0020 \end{array}

Nil

\begin{array}{lcl} NIL & ::= & nil \end{array}

Boolean

\begin{array}{lcl} BOOLEAN & ::= & true ∣ false \end{array}

Number

There is no distinction between unsigned and signed integers.

\begin{array}{lcl} INTEGER & ::= & DEC_INTEGER \\ ∣ & BIN_INTEGER \\ ∣ & OCT_INTEGER \\ ∣ & HEX_INTEGER \\ DEC_INTEGER & ::= & (0 ∣ \dots ∣ 9)^{+} \\ BIN_INTEGER & ::= & 0b (0 ∣ \dots ∣ 1)^{+} \\ OCT_INTEGER & ::= & 0o (0 ∣ \dots ∣ 7)^{+} \\ HEX_INTEGER & ::= & 0x (0 ∣ \dots ∣ 9 ∣ a ∣ \dots ∣ f ∣ A \dots ∣ F)^{+} \\ FLOAT & ::= & DEC_INTEGER ’.’ \sim [’.’] \\ ∣ & DEC_INTEGER ’.’ DEC_INTEGER \\ ∣ & ’.’ DEC_INTEGER \end{array}

String

\begin{array}{lcl} STRING & ::= & STRING_SINGLE \\ ∣ & STRING_DOUBLE \\ STRING_SINGLE & ::= & ’ {STRING_SINGLE_CHAR}^{*} ’ \\ STRING_DOUBLE & ::= & " {STRING_DOUBLE_CHAR}^{*} " \\ STRING_SINGLE_CHAR & ::= & \sim (\ ∣ ’) ∣ \ (n ∣ r ∣ t ∣ ’ ∣ \) \\ STRING_DOUBLE_CHAR & ::= & \sim (\ ∣ " ∣ #) ∣ ’#’ \sim [’{’] \\ ∣ & \ (n ∣ r ∣ t ∣ " ∣ \ ∣ ’#{’) \end{array}

Template String

\begin{array}{lcl} TEMPLATE_STRING & ::= & TEMPLATE_STRING_HEAD E x p r (TEMPLATE_STRING_BODY E x p r)^{*} TEMPLATE_STRING_TAIL \\ TEMPLATE_STRING_HEAD & ::= & " {STRING_DOUBLE_CHAR}^{*} ’#{’ \\ TEMPLATE_STRING_BODY & ::= & ’}’ {STRING_DOUBLE_CHAR}^{*} ’#{’ \\ TEMPLATE_STRING_TAIL & ::= & ’}’ {STRING_DOUBLE_CHAR}^{*} " \end{array}

Identifiers

$XID_START$ and $XID_CONTINUE$ are defined in Unicode Standard Annex #31.^[1]

\begin{array}{lcl} IDENT_OR_KEYWORD & ::= XID_START {XID_CONTINUE}^{*} \end{array}

The below are every keyword in Dyn. Reserved keywrods are NOT used yet, but they are reserved for future use and treated as just normal keywords.

Lexeme	Symbol	Reserved
$KW_BREAK$	$break$	X
$KW_CONTINUE$	$continue$	X
$KW_ELSE$	$else$	X
$KW_EXPORT$	$export$	O
$KW_FALSE$	$false$	X
$KW_IF$	$if$	X
$KW_ITER$	$iter$	X
$KW_LET$	$let$	X
$KW_NIL$	$nil$	X
$KW_OF$	$of$	X
$KW_RETURN$	$return$	X
$KW_TRUE$	$true$	X
$KW_USE$	$use$	O

Punctuations

Lexeme	Symbol	Reserved
$RightBrace$	$}$	X
$PipePipe$	$\|\|$	X
$Pipe$	$\|$	X
$LeftBrace$	${$	X
$RightBracket$	$]$	X
$NewLine$	$\n$	X
$LeftBracket$	$[$	X
$At$	$@$	O
$RightAngledBracketEqual$	$>=$	X
$RightAngledBracket$	$>$	X
$EqualEqual$	$==$	X
$Equal$	$=$	X
$LeftAngledBracketEqual$	$<=$	X
$LeftAngledBracket$	$<$	X
$Colon$	$:$	X
$SlashEqual$	$/=$	X
$Slash$	$/$	X
$DotDot$	$..$	X
$Dot$	$.$	X
$Arrow$	$->$	X
$MinusEqual$	$-=$	X
$Minus$	$-$	X
$Comma$	$,$	X
$PlusEqual$	$+=$	X
$Plus$	$+$	X
$AsteriskEqual$	$*=$	X
$Asterisk$	$*$	X
$RightParenthesis$	$)$	X
$LeftParenthesis$	$($	X
$AndAnd$	$&&$	X
$PercentEqual$	$%=$	X
$Percent$	$%$	X
$BangEqual$	$!=$	X
$Bang$	$!$	X

Syntectic Structure

Literals

\begin{array}{lcl} L i t e r a l s & ::= & N i l L i t e r a l \\ ∣ & B o o l e a n L i t e r a l \\ ∣ & I n t e g e r L i t e r a l \\ ∣ & F l o a t L i t e r a l \\ ∣ & S t r i n g L i t e r a l \\ ∣ & A r r a y L i t e r a l \\ ∣ & R e c o r d L i t e r a l \\ ∣ & F u n c t i o n L i t e r a l \\ N i l L i t e r a l & ::= & NIL \\ B o o l e a n L i t e r a l & ::= & BOOLEAN \\ I n t e g e r L i t e r a l & ::= & INTEGER \\ F l o a t L i t e r a l & ::= & FLOAT \\ S t r i n g L i t e r a l & ::= & STRING \\ A r r a y L i t e r a l & ::= & [⟨ E x p r, ’,’ ⟩] \\ R e c o r d L i t e r a l & ::= & ’(’ ⟨ I d e n t ’:’ E x p r, ’,’ ⟩ ’)’ \end{array}

FunctionLiteral

\begin{array}{lcl} F u n c t i o n P a r a m e t e r s & ::= & ⟨ I d e n t, ’,’ ⟩ \\ F u n c t i o n L i t e r a l & ::= & (’(’ F u n c t i o n P a r a m e t e r s ’)’)^{?} -> E x p r \end{array}

https://www.unicode.org/reports/tr31/ ↩︎

Syntax Specification ​

Conventions ​

Lexical Structure ​

Characters ​

Comments ​

White Spaces ​

Nil ​

Boolean ​

Number ​

String ​

Template String ​

Identifiers ​

Punctuations ​

Syntectic Structure ​

Literals ​

FunctionLiteral ​