Meerkat parsers: a general parser combinator library for real programming languages

Presented at ScalaDays 2015, Amsterdam

http://event.scaladays.org/scaladays-amsterdam-2015#!#schedulePopupExtras-6892

Github repository: https://github.com/Anastassija/Meerkat

1. Meerkat Parsers Anastasia Izmaylova @IAnastassija & Ali Afroozeh @afruze
3. An expression language sealed trait E case class Add(l: E, r: E) extends E case class Mul(l: E, r: E) extends E case class Sub(l: E, r: E) extends E case class Div(l: E, r: E) extends E case class Neg(l: E) extends E case class Pow(l: E, r: E) extends E case class Num(n: Int) extends E
4. An expression language 1*2+3-(1+7+-8)^3
5. An expression language 1*2+3-(1+7+-8)^3 ((1*2)+3)-(((1+7)+(-8))^3)
6. An expression language 1*2+3-(1+7+-8)^3 ((1*2)+3)-(((1+7)+(-8))^3) Sub(Add(Mul(Num(1),Num(2)),Num(3)),Pow(Add(Add(Num(1),Num(7)),Neg(Num(8))),Num(3)))
7. An expression language E ::= E '+' E | E '*' E | E '-' E | E '/' E | '-' E | E '^' E | Num val E: Parser = E ~ '+' ~ E | E ~ '*' ~ E | E ~ '-' ~ E | E ~ '/' ~ E | '-' ~ E | E ~ '^' ~ E | Num BNF-like notation Combinators
8. Parsing as a search problem
9. Left recursion def E(i: Int)(implicit input: String): Result[Tree] = { // E ::= E + E E(i) flatMap { j => . . . // E * E . . . }
10. Left recursion def E(i: Int)(implicit input: String): Result[Tree] = { // E ::= E + E E(i) flatMap { j => . . . // E * E . . . } Left recursion in top-down parsing can lead to non-termination
11. E ::= '-' E | E '*' E | E '+' E | Num '*' > '+' Natural grammars
12. E ::= '-' E | E '*' E | E '+' E | Num E ::= E '+' T | T T ::= T '*' F | F F ::= '-' F | Num '*' > '+' Natural grammars
13. E ::= '-' E | E '*' E | E '+' E | Num E ::= E '+' T | T T ::= T '*' F | F F ::= '-' F | Num E ::= T E1 E1 ::= '+' T E1 | ε T ::= F T1 T1 ::= '*' F | ε F ::= '-' F | Num '*' > '+' Natural grammars
14. E ::= '-' E | E '*' E | E '+' E | Num E ::= E '+' T | T T ::= T '*' F | F F ::= '-' F | Num E ::= T E1 E1 ::= '+' T E1 | ε T ::= F T1 T1 ::= '*' F | ε F ::= '-' F | Num '*' > '+' Natural grammars
15. E ::= '-' E | E '*' E | E '+' E | Num E ::= E '+' T | T T ::= T '*' F | F F ::= '-' F | Num E ::= T E1 E1 ::= '+' T E1 | ε T ::= F T1 T1 ::= '*' F | ε F ::= '-' F | Num '*' > '+' Natural grammars
16. E ::= '-' E | E '*' E | E '+' E | Num E ::= E '+' T | T T ::= T '*' F | F F ::= '-' F | Num E ::= T E1 E1 ::= '+' T E1 | ε T ::= F T1 T1 ::= '*' F | ε F ::= '-' F | Num '*' > '+' Natural grammars
17. Backtracking schemes 1 2 3 2 3 4 3 4 5 5 6 A ::= a b | a c "ac"
18. Backtracking schemes Deterministic (LL(k)) 1 2 3 2 3 4 3 4 5 5 6 A ::= a b | a c "ac"
19. Backtracking schemes Deterministic (LL(k)) 1 2 3 2 3 4 3 4 5 5 6 A ::= a b | a c "ac"
20. Backtracking schemes Deterministic (LL(k)) 1 2 3 2 3 4 3 4 5 5 6 A ::= a b | a c "ac"
21. "abd" Backtracking schemes Local backtracking (PEG) 1 2 3 2 3 4 3 4 5 5 6 A ::= B d B ::= a | ab
22. "abd" Backtracking schemes Local backtracking (PEG) 1 2 3 2 3 4 3 4 5 5 6 A ::= B d B ::= a | ab
23. "abd" Backtracking schemes Local backtracking (PEG) 1 2 3 2 3 4 3 4 5 5 6 A ::= B d B ::= a | ab
24. "abd" Backtracking schemes Local backtracking (PEG) 1 2 3 2 3 4 3 4 5 5 6 A ::= B d B ::= a | ab
25. "abd" Backtracking schemes Local backtracking (PEG) 1 2 3 2 3 4 3 4 5 5 6 A ::= B d B ::= a | ab
26. Nondeterminism and Ambiguity 1*2+3 E E + E E * E 1 2 3
27. Nondeterminism and Ambiguity 1*2+3 E E + E E * E 1 2 3 E E * E E + E 1 2 3 1*(2+3) (1*2)+3
28. Expressivity Deterministic Local Full Left recursion Only LR No combinator ? ✓
29. Deterministic General vs. Adrian Johnstone
30. But general parsing alone is not enough
32. • Natural grammar
33. • Natural grammar • Near-linear on near-deterministic grammars
34. Operator Precedence
35. Expression = AssignmentExpression AssignmentExpression = ConditionalExpression | Assignment ConditionalExpression = ConditionalOrExpression | ConditionalOrExpression "?" Expression ":" ConditionalExpression ConditionalOrExpression = ConditionalAndExpression | ConditionalOrExpression "||" ConditionalAndExpression ConditionalAndExpression = InclusiveOrExpression | ConditionalAndExpression "&&" InclusiveOrExpression InclusiveOrExpression = ExclusiveOrExpression | InclusiveOrExpression "|" ExclusiveOrExpression ExclusiveOrExpression = AndExpression | ExclusiveOrExpression "^" AndExpression . . .
36. if (x > 10) { println(x) } Lexing and Parsing
37. if (x > 10) { println(x) } Lexer Lexing and Parsing
38. if (x > 10) { println(x) } Lexer IF ( ID > 10 ) { ID ( ID ) } Lexing and Parsing
39. if (x > 10) { println(x) } Lexer IF ( ID > 10 ) { ID ( ID ) } Lexing and Parsing Whitespace/ Comment
40. if (x > 10) { println(x) } Lexer IF ( ID > 10 ) { ID ( ID ) } Lexing and Parsing Whitespace/ Comment Longest Match
41. if (x > 10) { println(x) } Lexer IF ( ID > 10 ) { ID ( ID ) } Lexing and Parsing Whitespace/ Comment Longest Match Keyword Reservation
42. if (x > 10) { println(x) } Lexer IF ( ID > 10 ) { ID ( ID ) } Lexing and Parsing Whitespace/ Comment Longest Match Keyword Reservation Scannerless Parsing
43. Context-sensitivity • Indentation-sensitive languages • Data protocols
44. Context-sensitivity • Indentation-sensitive languages • Data protocols Data-dependent parsing
45. Meet the Meerkats! Disambiguation Filters General Parsing Combinator-style Parsing
46. Best of both worlds Parser Generators Parser Combinators Flexibility, extensibility Left recursion Cubic bound Operator precedence Scannerless parsing
49. A. Afroozeh and A. Izmaylova, Faster, Practical GLL Parsing, CC’15
50. Shared Packed Parse Forest (SPPF) S ::= 'a' S 'b' | 'a' S | 's' "aasb" S, 0, 4 a, 0, 1 S, 1, 3 b, 3, 4 a, 1, 2 S, 2, 3 s, 2, 3 S, 1, 4 S, 0, 4 a, 0, 1 S, 2, 3 s, 2, 3 a, 1, 2 b, 3, 4
51. Shared Packed Parse Forest (SPPF) S ::= 'a' S 'b' | 'a' S | 's' "aasb" S, 0, 4 a, 0, 1 S, 1, 3 b, 3, 4 a, 1, 2 S, 2, 3 s, 2, 3 S, 1, 4 S, 0, 4 a, 0, 1 S, 2, 3 s, 2, 3 a, 1, 2 b, 3, 4 s, 2, 3 s, 2, 3 Figure 1: Two parse trees (left) and their corresponding SPPF (r To enable general context-free parsing in O(n3) without manu ing the grammar, Scott and Johnstone [18] introduced the notio SPPFs, which use additional intermediate nodes. Intermediate the form (L, i, j) where L is a grammar position and i and j are extents. Grammar positions for intermediate nodes are of the fo where |↵| >= 2. For example, S ::= aS · b for the rule S ::= aSb. version of SPPF in Figure 1 is shown in Figure 2. Intermediate similar to nonterminal nodes, can be ambiguous, in which case h one packed nodes as children. S, 0, 4 a, 0, 1 S, 1, 3 b, 3, 4 a, 1, 2 S, 2, 3 s, 2, 3 S, 1, 4 S ::= aS · b, 0, 3 S ::= aS · b, 1, 3 Figure 2: Binarized SPPF Packed nodes in a binarized SPPF are of the form (L, k), where L
52. Parse forest representation sealed trait Tree case class Appl(r: Rule, ts: Seq[Tree]) extends Tree case class Amb(ts: Set[Tree]) extends Tree case class Terminal(name: String) extends Tree ASF+SDF Rascal Spoofax
53. Parse forest representation Amb S ::= a S b S ::= a S "a" S ::= a S "b" "a" S ::= s "s" "a" S ::= a S b "a" S ::= s "b" "s" S ::= 'a' S 'b' | 'a' S | 's' "aasb"
54. Basic Parsers type Parser = (Input,Int,SPPFLookup) => Result[SPPFNode] trait Result[+T] extends ((T => Unit) => Unit) { def map[U](f: T => U): Result[U] def flatMap[U](f: T => Result[U]): Result[U] def orElse[U >: T](r: Result[U]): Result[U] }
55. val E: Nonterminal = syn ( E ~ '*' ~ E | E ~ '+' ~ E | Num ) Basic Parsers
56. val E: Nonterminal = syn ( E ~ '*' ~ E | E ~ '+' ~ E | Num ) Basic Parsers Tony Sloane, dsinfo library
57. val E: Nonterminal = syn ( E ~ '*' ~ E | E ~ '+' ~ E | Num ) 1+2*3 Basic Parsers Tony Sloane, dsinfo library
58. val E: Nonterminal = syn ( E ~ '*' ~ E | E ~ '+' ~ E | Num ) Amb E ::= E * E E ::= E + E E ::= E + E "*" E ::= Num E ::= Num "+" E ::= Num Num ::= [0-9] "1" Num ::= [0-9] "2" Num ::= [0-9] "3" E ::= Num "+" E ::= E * E Num ::= [0-9] "1" E ::= Num "*" E ::= Num Num ::= [0-9] "2" Num ::= [0-9] "3" 1+2*3 Basic Parsers Tony Sloane, dsinfo library
59. Operator parsers val E: Nonterminal = syn ( E ~ '*' ~ E | E ~ '+' ~ E | Num )
60. Operator parsers val E: OperatorNonterminal = syn ( E ~ '*' ~ E | E ~ '+' ~ E | Num )
61. Operator parsers val E: OperatorNonterminal = syn ( left { E ~ '*' ~ E } |> left { E ~ '+' ~ E } | Num )
62. Operator parsers val E: OperatorNonterminal = syn ( left { E ~ '*' ~ E } |> left { E ~ '+' ~ E } | Num )
63. Operator parsers val E: OperatorNonterminal = syn ( left { E ~ '*' ~ E } |> left { E ~ '+' ~ E } | Num )
64. Operator parsers type OperatorNonterminal = (Int,Int) => Nonterminal val E: OperatorNonterminal = syn ( left { E ~ '*' ~ E } |> left { E ~ '+' ~ E } | Num )
65. Operator parsers E(l,r) = [2>=l,2>=r] E(2,2) '*' E(3,3) // 2 | [1>=l,1>=r] E(0,0) '+' E(2,2) // 1 | Num type OperatorNonterminal = (Int,Int) => Nonterminal val E: OperatorNonterminal = syn ( left { E ~ '*' ~ E } |> left { E ~ '+' ~ E } | Num )
66. Operator parsers val E: OperatorNonterminal = syn ( left { E ~ '*' ~ E } |> left { E ~ '+' ~ E } | Num ) E(0,0) ::= E(1,1) + E(2,2) E(1,1) ::= Num "+" E(2,2) ::= E(2,2) * E(3,3) Num ::= [0-9] "1" E(2,2) ::= Num "*" E(3,3) ::= Num Num ::= [0-9] "2" Num ::= [0-9] "3"
67. Semantic actions val E: OperatorNonterminal & Int = syn ( '-' ~ E & { x => -x } |> left { E ~ '*' ~ E } & { case x~y => x*y } |> left { E ~ '+' ~ E } & { case x~y => x+y } | Num ^ { toInt(_) } )
68. Semantic actions val E: OperatorNonterminal & Int = syn ( '-' ~ E & { x => -x } |> left { E ~ '*' ~ E } & { case x~y => x*y } |> left { E ~ '+' ~ E } & { case x~y => x+y } | Num ^ { toInt(_) } )
69. Semantic actions val E: OperatorNonterminal & Int = syn ( '-' ~ E & { x => -x } |> left { E ~ '*' ~ E } & { case x~y => x*y } |> left { E ~ '+' ~ E } & { case x~y => x+y } | Num ^ { toInt(_) } )
70. Semantic actions val E: OperatorNonterminal & Int = syn ( '-' ~ E & { x => -x } |> left { E ~ '*' ~ E } & { case x~y => x*y } |> left { E ~ '+' ~ E } & { case x~y => x+y } | Num ^ { toInt(_) } )
71. Semantic actions val E: OperatorNonterminal & Int = syn ( '-' ~ E & { x => -x } |> left { E ~ '*' ~ E } & { case x~y => x*y } |> left { E ~ '+' ~ E } & { case x~y => x+y } | Num ^ { toInt(_) } )
72. Semantic actions val E: OperatorNonterminal & Int = syn ( '-' ~ E & { x => -x } |> left { E ~ '*' ~ E } & { case x~y => x*y } |> left { E ~ '+' ~ E } & { case x~y => x+y } | Num ^ { toInt(_) } ) Executed post-parse!
73. Whitespace/Comment if (x > 10 ) { println(x) }
74. Whitespace/Comment if (x > 10 ) { println(x) }
75. Whitespace/Comment def ~ (p: Symbol)(implicit layout: Layout): Sequence if (x > 10 ) { println(x) }
76. Whitespace/Comment def ~ (p: Symbol)(implicit layout: Layout): Sequence def ~~ (p: Symbol): Sequence if (x > 10 ) { println(x) }
77. Character-level disambiguation filters val Id = syn ( ('a' -- 'z').+ ) if (x > 10 ) { println(x) }
78. Character-level disambiguation filters val Id = syn ( ('a'--'z').+ \ ("if") ) if (x > 10 ) { println(x) }
79. Character-level disambiguation filters val Id = syn ( ('a'--'z').+ \ ("if") .!>> ("[a-z]".r) ) if (x > 10 ) { println(x) }
80. type DDParser[T] = (Input,Int,SPPFLookup) => Result[(SPPFNode,T)] Data-dependent parsers
81. type DDParser[T] = (Input,Int,SPPFLookup) => Result[(SPPFNode,T)] Data-dependent parsers
82. type DDParser[T] = (Input,Int,SPPFLookup) => Result[(SPPFNode,T)] val L8 = syn ( '~{' ~ Num ~ '+'.? ~ '}' ~ Octet.* ) ~{ 5 } X X X X X Data-dependent parsers
83. type DDParser[T] = (Input,Int,SPPFLookup) => Result[(SPPFNode,T)] val L8 = syn ( '~{' ~ Num ~ '+'.? ~ '}' ~ Octet.* ) def Octets(n: Int, p: Nonterminal) = n match { case 0 => syn ( epsilon ) case 1 => syn ( p ) case _ => syn ( (1 to n-2).foldLeft(p ~ p)((q,_) => q ~ p) ) } ~{ 5 } X X X X X Data-dependent parsers
84. type DDParser[T] = (Input,Int,SPPFLookup) => Result[(SPPFNode,T)] def Octets(n: Int, p: Nonterminal) = n match { case 0 => syn ( epsilon ) case 1 => syn ( p ) case _ => syn ( (1 to n-2).foldLeft(p ~ p)((q,_) => q ~ p) ) } val L8 = syn ( '~{' ~ Num.map(toInt) ~ '+'.? ~ '}' ~ Octet.* ) ~{ 5 } X X X X X Data-dependent parsers
85. type DDParser[T] = (Input,Int,SPPFLookup) => Result[(SPPFNode,T)] def Octets(n: Int, p: Nonterminal) = n match { case 0 => syn ( epsilon ) case 1 => syn ( p ) case _ => syn ( (1 to n-2).foldLeft(p ~ p)((q,_) => q ~ p) ) } val L8 = syn ( '~{' ~ Num.map(toInt) ~ '+'.? ~ '}' ~>> {Octets(_,Octet)} ) ~{ 5 } X X X X X Data-dependent parsers
86. Case study: expression language val E: OperatorNonterminal & E = syn ( right { E ~ "^" ~ E } & { case x~y => Pow(x, y) } |> "-" ~ E & { Neg(_) } |> left ( E ~ "*" ~ E & { case x~y => Mul(x, y) } | E ~ "/" ~ E & { case x~y => Div(x, y) } ) |> left ( E ~ "+" ~ E & { case x~y => Add(x, y) } | E ~ "-" ~ E & { case x~y => Sub(x, y) } ) | "(" ~ E ~ ")" | "[0-9]".r ^ { s => Num(toInt(s)) } ) sealed trait E case class Add(l: E, r: E) extends E case class Mul(l: E, r: E) extends E case class Sub(l: E, r: E) extends E case class Div(l: E, r: E) extends E case class Neg(l: E) extends E case class Pow(l: E, r: E) extends E case class Num(n: Int) extends E
87. Case study: expression language val E: OperatorNonterminal & E = syn ( right { E ~ "^" ~ E } & { case x~y => Pow(x, y) } |> "-" ~ E & { Neg(_) } |> left ( E ~ "*" ~ E & { case x~y => Mul(x, y) } | E ~ "/" ~ E & { case x~y => Div(x, y) } ) |> left ( E ~ "+" ~ E & { case x~y => Add(x, y) } | E ~ "-" ~ E & { case x~y => Sub(x, y) } ) | "(" ~ E ~ ")" | "[0-9]".r ^ { s => Num(toInt(s)) } ) sealed trait E case class Add(l: E, r: E) extends E case class Mul(l: E, r: E) extends E case class Sub(l: E, r: E) extends E case class Div(l: E, r: E) extends E case class Neg(l: E) extends E case class Pow(l: E, r: E) extends E case class Num(n: Int) extends E
88. Case study: expression language val = syn ( right { E ~ |> |> left ( E ~ | E ~ |> left ( E ~ | E ~ | | ) sealed case case case case case case case Associativity groups
89. Case study: expression language val = syn ( right { E ~ |> |> left ( E ~ | E ~ |> left ( E ~ | E ~ | | ) sealed case case case case case case case Associativity groups Other character-level filters
90. Case study: expression language val = syn ( right { E ~ |> |> left ( E ~ | E ~ |> left ( E ~ | E ~ | | ) sealed case case case case case case case Associativity groups Other character-level filters EBNF constructs
91. val Expression: OperatorNonterminal = syn ( Expression ~ "." ~ Identifier | Expression ~ "." ~ "this" | Expression ~ "." ~ "new" ~ TypeArguments.? ~ Identifier ~ TypeArgumentsOrDiamond.? ~ "(" ~ ArgumentList.? ~ ")" ~ ClassBody.? | Expression ~ "." ~ NonWildTypeArguments ~ ExplicitGenericInvocationSuffix | Expression ~ "." ~ "super" ~ ("." ~ Identifier).!.? ~ Arguments | Type ~ "." ~ "class" | "void" ~ "." ~ "class" | Expression ~ "(" ~ ArgumentList.? ~ ")" | Expression ~ "[" ~ Expression ~ "]" |> Expression ~ "++" | Expression ~ "--" |> "+".!>>("+") ~ Expression | "-".!>>("-") ~ Expression | "++" ~ Expression | "--" ~ Expression | "!" ~ Expression | "~" ~ Expression | "new" ~ ClassInstanceCreationExpression | "new" ~ ArrayCreationExpression | "(" ~ PrimitiveType ~ ")" ~ Expression | "(" ~ ReferenceType ~ ")" ~ Expression |> left ( Expression ~ "*" ~ Expression | Expression ~ "/" ~ Expression | Expression ~ "%" ~ Expression ) |> left ( Expression ~ "+".!>>("+") ~ Expression | Expression ~ "-".!>>("-") ~ Expression ) |> left ( Expression ~ "<<" ~ Expression | Expression ~ ">>".!>>(">") ~ Expression | Expression ~ ">>>" ~ Expression ) |> left ( Expression ~ "<".!>>("[=<]".r) ~ Expression | Expression ~ ">".!>>("[=>]".r) ~ Expression | Expression ~ "<=" ~ Expression | Expression ~ ">=" ~ Expression | Expression ~ "instanceof" ~ Type ) |> left ( Expression ~ "==" ~ Expression | Expression ~ "!=" ~ Expression ) |> Expression ~ "&".!>>("&") ~ Expression |> Expression ~ "^" ~ Expression |> Expression ~ "|".!>>("|") ~ Expression |> Expression ~ "&&" ~ Expression |> Expression ~ "||" ~ Expression |> Expression ~ "?" ~ Expression ~ ":" ~ Expression |> Expression ~ AssignmentOperator ~ Expression | "(" ~ Expression ~ ")" | Primary)
92. val Primary: Nonterminal = syn ( PrimaryNoNewArray | ArrayCreationExpression ) val PrimaryNoNewArray: Nonterminal = syn ( Literal | Type ~ "." ~ "class" | "void" ~ "." ~ "class" | "this" | ClassName ~ "." ~ "this" | "(" ~ Expression ~ ")" | ClassInstanceCreationExpression | FieldAccess | MethodInvocation | ArrayAccess ) val Literal: Nonterminal = syn ( IntegerLiteral | FloatingPointLiteral | BooleanLiteral | CharacterLiteral | StringLiteral | NullLiteral ) val IntegerLiteral: Nonterminal = syn ( DecimalIntegerLiteral.!>>(".") | HexIntegerLiteral.!>>(".") | OctalIntegerLiteral | BinaryIntegerLiteral ) val FloatingPointLiteral: Nonterminal = syn ( DecimalFloatingPointLiteral | HexadecimalFloatingPointLiteral ) val ClassInstanceCreationExpression: Nonterminal = syn ( "new" ~ TypeArguments.? ~ TypeDeclSpecifier ~ TypeArguments | (Primary | QualifiedIdentifier).! ~ "." ~ "new" ~ TypeArgum ) val TypeArgumentsOrDiamond: Nonterminal = syn ( "<" ~ ">" | TypeArguments ) val ArgumentList: Nonterminal = syn (Expression.+(",")) val ArrayCreationExpression: Nonterminal = syn ( "new" ~ (PrimitiveType | ReferenceType).! ~ DimExpr.+ ~ ("[ val Expression: OperatorNonterminal = syn ( Expression ~ "." ~ Identifier | Expression ~ "." ~ "this" | Expression ~ "." ~ "new" ~ TypeArguments.? ~ Identifier ~ TypeArgumentsOrDiamond.? ~ "(" ~ ArgumentList.? ~ ")" ~ ClassBody.? | Expression ~ "." ~ NonWildTypeArguments ~ ExplicitGenericInvocationSuffix | Expression ~ "." ~ "super" ~ ("." ~ Identifier).!.? ~ Arguments | Type ~ "." ~ "class" | "void" ~ "." ~ "class" | Expression ~ "(" ~ ArgumentList.? ~ ")" | Expression ~ "[" ~ Expression ~ "]" |> Expression ~ "++" | Expression ~ "--" |> "+".!>>("+") ~ Expression | "-".!>>("-") ~ Expression | "++" ~ Expression | "--" ~ Expression | "!" ~ Expression | "~" ~ Expression | "new" ~ ClassInstanceCreationExpression | "new" ~ ArrayCreationExpression | "(" ~ PrimitiveType ~ ")" ~ Expression | "(" ~ ReferenceType ~ ")" ~ Expression |> left ( Expression ~ "*" ~ Expression | Expression ~ "/" ~ Expression | Expression ~ "%" ~ Expression ) |> left ( Expression ~ "+".!>>("+") ~ Expression | Expression ~ "-".!>>("-") ~ Expression ) |> left ( Expression ~ "<<" ~ Expression | Expression ~ ">>".!>>(">") ~ Expression | Expression ~ ">>>" ~ Expression ) |> left ( Expression ~ "<".!>>("[=<]".r) ~ Expression | Expression ~ ">".!>>("[=>]".r) ~ Expression | Expression ~ "<=" ~ Expression | Expression ~ ">=" ~ Expression | Expression ~ "instanceof" ~ Type ) |> left ( Expression ~ "==" ~ Expression | Expression ~ "!=" ~ Expression ) |> Expression ~ "&".!>>("&") ~ Expression |> Expression ~ "^" ~ Expression |> Expression ~ "|".!>>("|") ~ Expression |> Expression ~ "&&" ~ Expression |> Expression ~ "||" ~ Expression |> Expression ~ "?" ~ Expression ~ ":" ~ Expression |> Expression ~ AssignmentOperator ~ Expression | "(" ~ Expression ~ ")" | Primary)
93. ) val InclusiveOrExpression: Nonterminal = syn ( ExclusiveOrExpression | InclusiveOrExpression ~ "|" ~ ExclusiveOrExpression ) val ConditionalAndExpression: Nonterminal = syn ( InclusiveOrExpression | ConditionalAndExpression ~ "&&" ~ InclusiveOrExpression ) val ConditionalOrExpression: Nonterminal = syn ( ConditionalAndExpression | ConditionalOrExpression ~ "||" ~ ConditionalAndExpression ) val ConditionalExpression: Nonterminal = syn ( ConditionalOrExpression | ConditionalOrExpression ~ "?" ~ Expression ~ ":" ~ Conditio ) val AssignmentExpression: Nonterminal = syn ( ConditionalExpression | Assignment ) val Assignment: Nonterminal = syn ( LeftHandSide ~ AssignmentOperator ~ AssignmentExpression ) val LeftHandSide: Nonterminal = syn ( ExpressionName | "(" ~ LeftHandSide ~ ")" | FieldAccess | ArrayAccess ) val AssignmentOperator: Nonterminal = syn ( "=" | "+=" | "-=" | "*=" | "/=" | "&=" | "|=" | "^=" | "%=" | "<<=" | ">>=" | ">>>=" ) val Expression: Nonterminal = syn ( AssignmentExpression ) val Expression: OperatorNonterminal = syn ( Expression ~ "." ~ Identifier | Expression ~ "." ~ "this" | Expression ~ "." ~ "new" ~ TypeArguments.? ~ Identifier ~ TypeArgumentsOrDiamond.? ~ "(" ~ ArgumentList.? ~ ")" ~ ClassBody.? | Expression ~ "." ~ NonWildTypeArguments ~ ExplicitGenericInvocationSuffix | Expression ~ "." ~ "super" ~ ("." ~ Identifier).!.? ~ Arguments | Type ~ "." ~ "class" | "void" ~ "." ~ "class" | Expression ~ "(" ~ ArgumentList.? ~ ")" | Expression ~ "[" ~ Expression ~ "]" |> Expression ~ "++" | Expression ~ "--" |> "+".!>>("+") ~ Expression | "-".!>>("-") ~ Expression | "++" ~ Expression | "--" ~ Expression | "!" ~ Expression | "~" ~ Expression | "new" ~ ClassInstanceCreationExpression | "new" ~ ArrayCreationExpression | "(" ~ PrimitiveType ~ ")" ~ Expression | "(" ~ ReferenceType ~ ")" ~ Expression |> left ( Expression ~ "*" ~ Expression | Expression ~ "/" ~ Expression | Expression ~ "%" ~ Expression ) |> left ( Expression ~ "+".!>>("+") ~ Expression | Expression ~ "-".!>>("-") ~ Expression ) |> left ( Expression ~ "<<" ~ Expression | Expression ~ ">>".!>>(">") ~ Expression | Expression ~ ">>>" ~ Expression ) |> left ( Expression ~ "<".!>>("[=<]".r) ~ Expression | Expression ~ ">".!>>("[=>]".r) ~ Expression | Expression ~ "<=" ~ Expression | Expression ~ ">=" ~ Expression | Expression ~ "instanceof" ~ Type ) |> left ( Expression ~ "==" ~ Expression | Expression ~ "!=" ~ Expression ) |> Expression ~ "&".!>>("&") ~ Expression |> Expression ~ "^" ~ Expression |> Expression ~ "|".!>>("|") ~ Expression |> Expression ~ "&&" ~ Expression |> Expression ~ "||" ~ Expression |> Expression ~ "?" ~ Expression ~ ":" ~ Expression |> Expression ~ AssignmentOperator ~ Expression | "(" ~ Expression ~ ")" | Primary)
94. Operator precedence Left recursion Parse Forest Semantic actions Data- dependency Meerkat Parsers A @IAnastassija & A @afruze Scannerless Parsing https://github.com/Anastassija/Meerkat