Lower-case production names are used to identify lexical tokens.
Non-terminals are in CamelCase. Lexical symbols are enclosed in
-double quotes "" (the double quote symbol is written as
-'"').
+double "" or back quotes ``.
-The form "a ... b" represents the set of characters from
+The form a ... b represents the set of characters from
a through b as alternatives.
The following terms are used to denote specific Unicode character classes:
-+unicode_char = /* an arbitrary Unicode code point */ . +unicode_letter = /* a Unicode code point classified as "Letter" */ . +capital_letter = /* a Unicode code point classified as "Letter, uppercase" */ . +unicode_digit = /* a Unicode code point classified as "Digit" */ . +(The Unicode Standard, Section 4.5 General Category - Normative.) @@ -112,8 +111,8 @@ The following terms are used to denote specific Unicode character classes:
The underscore character _ (U+005F) is considered a letter.
-
-
+ +letter = unicode_letter | "_" . decimal_digit = "0" ... "9" . octal_digit = "0" ... "7" . @@ -152,7 +151,7 @@ Identifiers name program entities such as variables and types. An identifier is a sequence of one or more letters and digits. The first character in an identifier must be a letter. -+identifier = letter { letter | unicode_digit } .@@ -199,7 +198,7 @@ sets a non-decimal base:0for octal,0xor0Xfor hexadecimal. In hexadecimal literals, lettersa-fandA-Frepresent values 10 through 15. -+int_lit = decimal_lit | octal_lit | hex_lit . decimal_lit = ( "1" ... "9" ) { decimal_digit } . octal_lit = "0" { octal_digit } . @@ -223,7 +222,7 @@ followed by an optionally signed decimal exponent. One of the integer part or the fractional part may be elided; one of the decimal point or the exponent may be elided. -+float_lit = decimals "." [ decimals ] [ exponent ] | decimals exponent | "." decimals [ exponent ] . @@ -312,16 +311,16 @@ After a backslash, certain single-character escapes represent special values:All other sequences are illegal inside character literals.
-+char_lit = "'" ( unicode_value | byte_value ) "'" . unicode_value = unicode_char | little_u_value | big_u_value | escaped_char . byte_value = octal_byte_value | hex_byte_value . -octal_byte_value = "\" octal_digit octal_digit octal_digit . -hex_byte_value = "\" "x" hex_digit hex_digit . -little_u_value = "\" "u" hex_digit hex_digit hex_digit hex_digit . -big_u_value = "\" "U" hex_digit hex_digit hex_digit hex_digit +octal_byte_value = `\` octal_digit octal_digit octal_digit . +hex_byte_value = `\` "x" hex_digit hex_digit . +little_u_value = `\` "u" hex_digit hex_digit hex_digit hex_digit . +big_u_value = `\` "U" hex_digit hex_digit hex_digit hex_digit hex_digit hex_digit hex_digit hex_digit . -escaped_char = "\" ( "a" | "b" | "f" | "n" | "r" | "t" | "v" | "\" | "'" | """ ) . +escaped_char = `\` ( "a" | "b" | "f" | "n" | "r" | "t" | "v" | `\` | "'" | `"` ) .'a' @@ -379,7 +378,7 @@ U+00FF. A sequence of string literals is concatenated to form a single string. -+StringLit = string_lit { string_lit } . string_lit = raw_string_lit | interpreted_string_lit . raw_string_lit = "`" { unicode_char } "`" . @@ -430,7 +429,7 @@ type. A type may be specified by a (possibly qualified) type name which composes a new type from previously declared types. -+Type = TypeName | TypeLit | "(" Type ")" . TypeName = QualifiedIdent. TypeLit = ArrayType | StructType | PointerType | FunctionType | InterfaceType | @@ -568,7 +567,7 @@ type, called the element type, which must be complete negative. -+ArrayType = "[" ArrayLength "]" ElementType . ArrayLength = Expression . ElementType = CompleteType . @@ -598,7 +597,7 @@ type denotes the set of all slices of arrays of its element type. A slice value may benil. -+SliceType = "[" "]" ElementType .@@ -674,7 +673,7 @@ an identifier and type for each field. Within a struct, field identifiers must be unique and field types must be complete (§Types). -+StructType = "struct" "{" [ FieldDeclList ] "}" . FieldDeclList = FieldDecl { ";" FieldDecl } [ ";" ] . FieldDecl = (IdentifierList CompleteType | [ "*" ] TypeName) [ Tag ] . @@ -775,7 +774,7 @@ type, called the base type of the pointer. A pointer value may benil. -+PointerType = "*" BaseType . BaseType = Type .@@ -793,7 +792,7 @@ and result types. A function value may benil. -+FunctionType = "func" Signature . Signature = Parameters [ Result ] . Result = Parameters | CompleteType . @@ -842,7 +841,7 @@ that is any superset of the interface. Such a type is said to implement the interface. An interface value may benil. -+InterfaceType = "interface" "{" [ MethodSpecList ] "}" . MethodSpecList = MethodSpec { ";" MethodSpec } [ ";" ] . MethodSpec = IdentifierList Signature | InterfaceTypeName . @@ -943,7 +942,7 @@ A map value may benil. -+MapType = "map" "[" KeyType "]" ValueType . KeyType = CompleteType . ValueType = CompleteType . @@ -1000,7 +999,7 @@ specified element type. The element type must be complete (§Types). A value of channel type may benil. -+ChannelType = Channel | SendChannel | RecvChannel . Channel = "chan" ValueType . SendChannel = "chan" "<-" ValueType . @@ -1242,7 +1241,7 @@ a variable or function and specifies properties such as its type. Every identifier in a program must be declared. -+Declaration = ConstDecl | TypeDecl | VarDecl | FunctionDecl | MethodDecl .@@ -1349,7 +1348,7 @@ the left is bound to value of the nth expression on the right. -+ConstDecl = "const" ( ConstSpec | "(" [ ConstSpecList ] ")" ) . ConstSpecList = ConstSpec { ";" ConstSpec } [ ";" ] . ConstSpec = IdentifierList [ [ CompleteType ] "=" ExpressionList ] . @@ -1465,7 +1464,7 @@ A type declaration binds an identifier, the type name, to a new type. TODO: what exactly is a "new type"? -+TypeDecl = "type" ( TypeSpec | "(" [ TypeSpecList ] ")" ) . TypeSpecList = TypeSpec { ";" TypeSpec } [ ";" ] . TypeSpec = identifier ( Type | "struct" | "interface" ) . @@ -1498,7 +1497,7 @@ A variable declaration creates a variable, binds an identifier to it and gives it a type and optionally an initial value. The type must be complete (§Types). -+VarDecl = "var" ( VarSpec | "(" [ VarSpecList ] ")" ) . VarSpecList = VarSpec { ";" VarSpec } [ ";" ] . VarSpec = IdentifierList ( CompleteType [ "=" ExpressionList ] | "=" ExpressionList ) . @@ -1546,7 +1545,7 @@ var f = 3.1415 // f has type float A short variable declaration uses the syntax -+SimpleVarDecl = IdentifierList ":=" ExpressionList .@@ -1603,7 +1602,7 @@ they can be used to declare local temporary variables (§Statements). A function declaration binds an identifier to a function (§Function types). -+FunctionDecl = "func" identifier Signature [ Block ] .@@ -1627,7 +1626,7 @@ Implementation restriction: Functions can only be declared at the package level. A method declaration binds an identifier to a method, which is a function with a receiver. -+MethodDecl = "func" Receiver identifier Signature [ Block ] . Receiver = "(" [ identifier ] [ "*" ] TypeName ")" .@@ -1742,7 +1741,7 @@ and a type. Operands denote the elementary values in an expression. -+Operand = Literal | QualifiedIdent | "(" Expression ")" . Literal = BasicLit | CompositeLit | FunctionLit . BasicLit = int_lit | float_lit | char_lit | StringLit . @@ -1766,7 +1765,7 @@ Constants have values that are known at compile time. A qualified identifier is an identifier qualified by a package name prefix. -+QualifiedIdent = [ ( LocalPackageName | PackageName ) "." ] identifier . LocalPackageName = identifier . PackageName = identifier . @@ -1802,7 +1801,7 @@ followed by a brace-bound list of composite elements. An element may be a single expression or a key-value pair. -+CompositeLit = LiteralType "{" [ ElementList ] "}" . LiteralType = StructType | ArrayType | "[" "..." "]" ElementType | SliceType | MapType | TypeName . @@ -1965,7 +1964,7 @@ A function literal represents an anonymous function. It consists of a specification of the function type and a function body. -+FunctionLit = FunctionType Block . Block = "{" StatementList "}" .@@ -1993,7 +1992,7 @@ as they are accessible.Primary expressions
-+PrimaryExpr = Operand | PrimaryExpr Selector | @@ -2414,7 +2413,7 @@ parameter is passed unchanged as an actual...parameter. Operators combine operands into expressions. -+Expression = UnaryExpr | Expression binary_op UnaryExpr . UnaryExpr = PrimaryExpr | unary_op UnaryExpr . @@ -3003,7 +3002,7 @@ ofyis not specified. Statements control execution. -+Statement = Declaration | EmptyStmt | LabeledStmt | SimpleStmt | GoStmt | ReturnStmt | BreakStmt | ContinueStmt | GotoStmt | @@ -3013,7 +3012,7 @@ Statement = SimpleStmt = ExpressionStmt | IncDecStmt | Assignment | SimpleVarDecl . StatementList = Statement { Separator Statement } . -Separator = [ ";" ] +Separator = [ ";" ] .@@ -3033,7 +3032,7 @@ which may be omitted only if the previous statement: The empty statement does nothing.
-+EmptyStmt = .@@ -3050,7 +3049,7 @@ A labeled statement may be the target of agoto,breakorcontinuestatement. -+LabeledStmt = Label ":" Statement . Label = identifier .@@ -3068,7 +3067,7 @@ can appear in statement context. -+ExpressionStmt = Expression .@@ -3086,7 +3085,7 @@ by the ideal numeric value 1. As with an assignment, the operand must be a variable, pointer indirection, field selector or index expression. -+IncDecStmt = Expression ( "++" | "--" ) .@@ -3103,7 +3102,7 @@ x-- x -= 1Assignments
-+Assignment = ExpressionList assign_op ExpressionList . assign_op = [ add_op | mul_op ] "=" . @@ -3182,7 +3181,7 @@ present, the "else" branch is executed. A missing condition is equivalent totrue. -+IfStmt = "if" [ [ SimpleStmt ] ";" ] [ Expression ] Block [ "else" Statement ] .@@ -3219,7 +3218,7 @@ inside the "switch" to determine which branch to execute. -+SwitchStmt = ExprSwitchStmt | TypeSwitchStmt .@@ -3249,7 +3248,7 @@ A missing expression is equivalent to the expressiontrue. -+ExprSwitchStmt = "switch" [ [ SimpleStmt ] ";" ] [ Expression ] "{" { ExprCaseClause } "}" . ExprCaseClause = ExprSwitchCase ":" [ StatementList ] . ExprSwitchCase = "case" ExpressionList | "default" . @@ -3306,7 +3305,7 @@ Cases then match literal types against the dynamic type of the expression in the type assertion. -+TypeSwitchStmt = "switch" [ [ SimpleStmt ] ";" ] TypeSwitchGuard "{" { TypeCaseClause } "}" . TypeSwitchGuard = identifier ":=" Expression "." "(" "type" ")" . TypeCaseClause = TypeSwitchCase ":" [ StatementList ] . @@ -3375,7 +3374,7 @@ A "for" statement specifies repeated execution of a block. The iteration is controlled by a condition, a "for" clause, or a "range" clause. -+ForStmt = "for" [ Condition | ForClause | RangeClause ] Block . Condition = Expression .@@ -3403,7 +3402,7 @@ it declares ends at the end of the statement (§Declarations and scope rules). -+ForClause = [ InitStmt ] ";" [ Condition ] ";" [ PostStmt ] . InitStmt = SimpleStmt . PostStmt = SimpleStmt . @@ -3439,7 +3438,7 @@ variable - or the current (index, element) or (key, value) pair to a pair of iteration variables - and then executes the block. -+RangeClause = ExpressionList ( "=" | ":=" ) "range" Expression .@@ -3518,7 +3517,7 @@ as an independent concurrent thread of control, or goroutine, within the same address space. -+GoStmt = "go" Expression .@@ -3542,7 +3541,7 @@ will proceed. It looks similar to a "switch" statement but with the cases all referring to communication operations. -+SelectStmt = "select" "{" { CommClause } "}" . CommClause = CommCase ":" StatementList . CommCase = "case" ( SendExpr | RecvExpr) | "default" . @@ -3615,7 +3614,7 @@ A "return" statement terminates execution of the containing function and optionally provides a result value or values to the caller. -+ReturnStmt = "return" [ ExpressionList ] .@@ -3685,7 +3684,7 @@ A "break" statement terminates execution of the innermost "for", "switch" or "select" statement. -+BreakStmt = "break" [ Label ].@@ -3711,7 +3710,7 @@ A "continue" statement begins the next iteration of the innermost "for" loop at the post statement (§For statements). -+ContinueStmt = "continue" [ Label ].@@ -3725,7 +3724,7 @@ The optional label is analogous to that of a "break" statement. A "goto" statement transfers control to the statement with the corresponding label. -+GotoStmt = "goto" Label .@@ -3760,7 +3759,7 @@ be used only as the final non-empty statement in a case or default clause in an expression "switch" statement. -+FallthroughStmt = "fallthrough" .@@ -3772,7 +3771,7 @@ A "defer" statement invokes a function whose execution is deferred to the moment the surrounding function returns. -+DeferStmt = "defer" Expression .@@ -4016,7 +4015,7 @@ package clause acts as a block for scoping (§Declarations and scope rules). -+SourceFile = PackageClause { ImportDecl [ ";" ] } { Declaration [ ";" ] } .@@ -4027,7 +4026,7 @@ A package clause begins each source file and defines the package to which the file belongs. -+PackageClause = "package" PackageName .@@ -4052,7 +4051,7 @@ the package. The file name may be relative to a repository of installed packages. -+ImportDecl = "import" ( ImportSpec | "(" [ ImportSpecList ] ")" ) . ImportSpecList = ImportSpec { ";" ImportSpec } [ ";" ] . ImportSpec = [ "." | PackageName ] PackageFileName .