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add switch statement to language reference
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Andrew Kelley
parent
890714b8ca
commit
17e574fec6
114
doc/langref.md
114
doc/langref.md
@ -30,139 +30,145 @@ zig | C equivalent | Description
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## Grammar
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```
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Root : many(TopLevelDecl) token(EOF)
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Root : many(TopLevelDecl) "EOF"
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TopLevelDecl : FnDef | ExternBlock | RootExportDecl | Import | ContainerDecl | VariableDeclaration
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VariableDeclaration : option(FnVisibleMod) (token(Var) | token(Const)) token(Symbol) (token(Eq) Expression | token(Colon) PrefixOpExpression option(token(Eq) Expression))
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VariableDeclaration : option(FnVisibleMod) ("var" | "const") "symbol" ("=" Expression | ":" PrefixOpExpression option("=" Expression))
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ContainerDecl : many(Directive) option(FnVisibleMod) (token(Struct) | token(Enum)) token(Symbol) token(LBrace) many(StructMember) token(RBrace)
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ContainerDecl : many(Directive) option(FnVisibleMod) ("struct" | "enum") "Symbol" "{" many(StructMember) "}"
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StructMember: StructField | FnDecl
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StructField : token(Symbol) option(token(Colon) Expression) token(Comma))
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StructField : "Symbol" option(":" Expression) ",")
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Import : many(Directive) token(Import) token(String) token(Semicolon)
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Import : many(Directive) "import" "String" ";"
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RootExportDecl : many(Directive) token(Export) token(Symbol) token(String) token(Semicolon)
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RootExportDecl : many(Directive) "export" "Symbol" "String" ";"
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ExternBlock : many(Directive) token(Extern) token(LBrace) many(FnDecl) token(RBrace)
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ExternBlock : many(Directive) "extern" "{" many(FnDecl) "}"
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FnProto : many(Directive) option(FnVisibleMod) token(Fn) token(Symbol) ParamDeclList option(PrefixOpExpression)
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FnProto : many(Directive) option(FnVisibleMod) "fn" "Symbol" ParamDeclList option(PrefixOpExpression)
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Directive : token(NumberSign) token(Symbol) token(LParen) token(String) token(RParen)
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Directive : "#" "Symbol" "(" "String" ")"
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FnVisibleMod : token(Pub) | token(Export)
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FnVisibleMod : "pub" | "export"
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FnDecl : FnProto token(Semicolon)
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FnDecl : FnProto ";"
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FnDef : FnProto token(FatArrow) Block
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FnDef : FnProto "=>" Block
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ParamDeclList : token(LParen) list(ParamDecl, token(Comma)) token(RParen)
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ParamDeclList : "(" list(ParamDecl, ",") ")"
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ParamDecl : option(token(NoAlias)) token(Symbol) token(Colon) PrefixOpExpression | token(Ellipsis)
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ParamDecl : option("noalias") "Symbol" ":" PrefixOpExpression | "..."
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Block : token(LBrace) list(option(Statement), token(Semicolon)) token(RBrace)
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Block : "{" list(option(Statement), ";") "}"
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Statement : Label | VariableDeclaration token(Semicolon) | NonBlockExpression token(Semicolon) | BlockExpression
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Statement : Label | VariableDeclaration ";" | NonBlockExpression ";" | BlockExpression
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Label: token(Symbol) token(Colon)
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Label: "Symbol" ":"
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Expression : BlockExpression | NonBlockExpression
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NonBlockExpression : ReturnExpression | AssignmentExpression
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AsmExpression : token(Asm) option(token(Volatile)) token(LParen) token(String) option(AsmOutput) token(RParen)
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AsmExpression : "asm" option("volatile") "(" "String" option(AsmOutput) ")"
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AsmOutput : token(Colon) list(AsmOutputItem, token(Comma)) option(AsmInput)
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AsmOutput : ":" list(AsmOutputItem, ",") option(AsmInput)
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AsmInput : token(Colon) list(AsmInputItem, token(Comma)) option(AsmClobbers)
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AsmInput : ":" list(AsmInputItem, ",") option(AsmClobbers)
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AsmOutputItem : token(LBracket) token(Symbol) token(RBracket) token(String) token(LParen) (token(Symbol) | token(Arrow) PrefixOpExpression) token(RParen)
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AsmOutputItem : "[" "Symbol" "]" "String" "(" ("Symbol" | "->" PrefixOpExpression) ")"
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AsmInputItem : token(LBracket) token(Symbol) token(RBracket) token(String) token(LParen) Expression token(RParen)
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AsmInputItem : "[" "Symbol" "]" "String" "(" Expression ")"
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AsmClobbers: token(Colon) list(token(String), token(Comma))
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AsmClobbers: ":" list("String", ",")
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UnwrapMaybeExpression : BoolOrExpression token(DoubleQuestionMark) BoolOrExpression | BoolOrExpression
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UnwrapMaybeExpression : BoolOrExpression "??" BoolOrExpression | BoolOrExpression
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AssignmentExpression : UnwrapMaybeExpression AssignmentOperator UnwrapMaybeExpression | UnwrapMaybeExpression
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AssignmentOperator : token(Eq) | token(TimesEq) | token(DivEq) | token(ModEq) | token(PlusEq) | token(MinusEq) | token(BitShiftLeftEq) | token(BitShiftRightEq) | token(BitAndEq) | token(BitXorEq) | token(BitOrEq) | token(BoolAndEq) | token(BoolOrEq)
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AssignmentOperator : "=" | "*=" | "/=" | "%=" | "+=" | "-=" | "<<=" | ">>=" | "&=" | "^=" | "|=" | "&&=" | "||="
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BlockExpression : IfExpression | Block | WhileExpression | ForExpression
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BlockExpression : IfExpression | Block | WhileExpression | ForExpression | SwitchExpression
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WhileExpression : token(While) token(LParen) Expression token(RParen) Expression
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SwitchExpression : "switch" "(" Expression ")" "{" many(SwitchProng) "}"
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ForExpression : token(For) token(LParen) Symbol token(Comma) Expression option(token(Comma) token(Symbol)) token(RParen) Expression
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SwitchProng : (list(SwitchItem, ",") | "else") option("(" "Symbol" ")") "=>" Expression ","
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BoolOrExpression : BoolAndExpression token(BoolOr) BoolOrExpression | BoolAndExpression
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SwitchItem : Expression | (Expression "..." Expression)
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ReturnExpression : token(Return) option(Expression)
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WhileExpression : "while" "(" Expression ")" Expression
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ForExpression : "for" "(" "Symbol" "," Expression option("," "Symbol") ")" Expression
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BoolOrExpression : BoolAndExpression "||" BoolOrExpression | BoolAndExpression
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ReturnExpression : "return" option(Expression)
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IfExpression : IfVarExpression | IfBoolExpression
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IfBoolExpression : token(If) token(LParen) Expression token(RParen) Expression option(Else)
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IfBoolExpression : "if" "(" Expression ")" Expression option(Else)
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IfVarExpression : token(If) token(LParen) (token(Const) | token(Var)) token(Symbol) option(token(Colon) PrefixOpExpression) Token(MaybeAssign) Expression token(RParen) Expression Option(Else)
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IfVarExpression : "if" "(" ("const" | "var") "Symbol" option(":" PrefixOpExpression) "?=" Expression ")" Expression Option(Else)
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Else : token(Else) Expression
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Else : "else" Expression
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BoolAndExpression : ComparisonExpression token(BoolAnd) BoolAndExpression | ComparisonExpression
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BoolAndExpression : ComparisonExpression "&&" BoolAndExpression | ComparisonExpression
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ComparisonExpression : BinaryOrExpression ComparisonOperator BinaryOrExpression | BinaryOrExpression
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ComparisonOperator : token(BoolEq) | token(BoolNotEq) | token(BoolLessThan) | token(BoolGreaterThan) | token(BoolLessEqual) | token(BoolGreaterEqual)
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ComparisonOperator : "==" | "!=" | "<" | ">" | "<=" | ">="
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BinaryOrExpression : BinaryXorExpression token(BinOr) BinaryOrExpression | BinaryXorExpression
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BinaryOrExpression : BinaryXorExpression "|" BinaryOrExpression | BinaryXorExpression
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BinaryXorExpression : BinaryAndExpression token(BinXor) BinaryXorExpression | BinaryAndExpression
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BinaryXorExpression : BinaryAndExpression "^" BinaryXorExpression | BinaryAndExpression
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BinaryAndExpression : BitShiftExpression token(Ampersand) BinaryAndExpression | BitShiftExpression
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BinaryAndExpression : BitShiftExpression "&" BinaryAndExpression | BitShiftExpression
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BitShiftExpression : AdditionExpression BitShiftOperator BitShiftExpression | AdditionExpression
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BitShiftOperator : token(BitShiftLeft) | token(BitShiftRight)
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BitShiftOperator : "<<" | ">>"
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AdditionExpression : MultiplyExpression AdditionOperator AdditionExpression | MultiplyExpression
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AdditionOperator : token(Plus) | token(Minus)
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AdditionOperator : "+" | "-"
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MultiplyExpression : CurlySuffixExpression MultiplyOperator MultiplyExpression | CurlySuffixExpression
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CurlySuffixExpression : PrefixOpExpression option(ContainerInitExpression)
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MultiplyOperator : token(Star) | token(Slash) | token(Percent)
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MultiplyOperator : "*" | "/" | "%"
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PrefixOpExpression : PrefixOp PrefixOpExpression | SuffixOpExpression
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SuffixOpExpression : PrimaryExpression option(FnCallExpression | ArrayAccessExpression | FieldAccessExpression | SliceExpression)
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FieldAccessExpression : token(Dot) token(Symbol)
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FieldAccessExpression : "." "Symbol"
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FnCallExpression : token(LParen) list(Expression, token(Comma)) token(RParen)
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FnCallExpression : "(" list(Expression, ",") ")"
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ArrayAccessExpression : token(LBracket) Expression token(RBracket)
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ArrayAccessExpression : "[" Expression "]"
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SliceExpression : token(LBracket) Expression token(Ellipsis) option(Expression) token(RBracket) option(token(Const))
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SliceExpression : "[" Expression "..." option(Expression) "]" option("const")
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ContainerInitExpression : token(LBrace) ContainerInitBody token(RBrace)
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ContainerInitExpression : "{" ContainerInitBody "}"
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ContainerInitBody : list(StructLiteralField, token(Comma)) | list(Expression, token(Comma))
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ContainerInitBody : list(StructLiteralField, ",") | list(Expression, ",")
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StructLiteralField : token(Dot) token(Symbol) token(Eq) Expression
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StructLiteralField : "." "Symbol" "=" Expression
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PrefixOp : token(Not) | token(Dash) | token(Tilde) | token(Star) | (token(Ampersand) option(token(Const))) | token(QuestionMark)
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PrefixOp : "!" | "-" | "~" | "*" | ("&" option("const")) | "?"
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PrimaryExpression : token(Number) | token(String) | token(CharLiteral) | KeywordLiteral | GroupedExpression | GotoExpression | BlockExpression | token(Symbol) | (token(AtSign) token(Symbol) FnCallExpression) | ArrayType | AsmExpression
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PrimaryExpression : "Number" | "String" | "CharLiteral" | KeywordLiteral | GroupedExpression | GotoExpression | BlockExpression | "Symbol" | ("@" "Symbol" FnCallExpression) | ArrayType | AsmExpression
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ArrayType : token(LBracket) option(Expression) token(RBracket) option(token(Const)) PrefixOpExpression
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ArrayType : "[" option(Expression) "]" option("const") PrefixOpExpression
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GotoExpression: token(Goto) token(Symbol)
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GotoExpression: "goto" "Symbol"
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GroupedExpression : token(LParen) Expression token(RParen)
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GroupedExpression : "(" Expression ")"
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KeywordLiteral : token(True) | token(False) | token(Null) | token(Break) | token(Continue)
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KeywordLiteral : "true" | "false" | "null" | "break" | "continue"
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```
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## Operator Precedence
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