1
0
mirror of https://github.com/golang/go synced 2024-11-11 18:51:37 -07:00

- replaced 's in productions everywhere with "s (we were inconsistent in

some places)
- removed extra []'s around switch decl/tag expression - not needed

SVN=112117
This commit is contained in:
Robert Griesemer 2008-03-11 16:02:46 -07:00
parent 213702a3e6
commit 7acb294d58

View File

@ -190,17 +190,18 @@ Here is a complete example Go program that implements a concurrent prime sieve:
Notation
----
The syntax is specified using Extended
Backus-Naur Form (EBNF). In particular:
The syntax is specified using Extended Backus-Naur Form (EBNF).
In particular:
- '' encloses lexical symbols
- | separates alternatives
- "" encloses lexical symbols (\" is used to denote a " in a symbol)
- | separates alternatives
- () used for grouping
- [] specifies option (0 or 1 times)
- {} specifies repetition (0 to n times)
A production may be referenced from various places in this document
but is usually defined close to its first use. Code examples are indented.
but is usually defined close to its first use. Productions and code
examples are indented.
Lower-case production names are used to identify productions that cannot
be broken by white space or comments; they are usually tokens. Other
@ -210,10 +211,10 @@ productions are in CamelCase.
Common productions
----
IdentifierList = identifier { ',' identifier } .
ExpressionList = Expression { ',' Expression } .
IdentifierList = identifier { "," identifier } .
ExpressionList = Expression { "," Expression } .
QualifiedIdent = [ PackageName '.' ] identifier .
QualifiedIdent = [ PackageName "." ] identifier .
PackageName = identifier .
@ -246,11 +247,11 @@ to refer to an arbitrary Unicode code point encoded in UTF-8.
Digits and Letters
----
octal_digit = { '0' | '1' | '2' | '3' | '4' | '5' | '6' | '7' } .
decimal_digit = { '0' | '1' | '2' | '3' | '4' | '5' | '6' | '7' | '8' | '9' } .
hex_digit = { '0' | '1' | '2' | '3' | '4' | '5' | '6' | '7' | '8' | '9' | 'a' |
'A' | 'b' | 'B' | 'c' | 'C' | 'd' | 'D' | 'e' | 'E' | 'f' | 'F' } .
letter = 'A' | 'a' | ... 'Z' | 'z' | '_' .
octal_digit = { "0" | "1" | "2" | "3" | "4" | "5" | "6" | "7" } .
decimal_digit = { "0" | "1" | "2" | "3" | "4" | "5" | "6" | "7" | "8" | "9" } .
hex_digit = { "0" | "1" | "2" | "3" | "4" | "5" | "6" | "7" | "8" | "9" | "a" |
"A" | "b" | "B" | "c" | "C" | "d" | "D" | "e" | "E" | "f" | "F" } .
letter = "A" | "a" | ... "Z" | "z" | "_" .
For simplicity, letters and digits are ASCII. We may in time allow
Unicode identifiers.
@ -337,13 +338,13 @@ variable or constant.
Floating point literals also represent an abstract, ideal floating
point value that is constrained only upon assignment.
int_lit = [ '+' | '-' ] unsigned_int_lit .
int_lit = [ "+" | "-" ] unsigned_int_lit .
unsigned_int_lit = decimal_int_lit | octal_int_lit | hex_int_lit .
decimal_int_lit = ( '1' | '2' | '3' | '4' | '5' | '6' | '7' | '8' | '9' )
decimal_int_lit = ( "1" | "2" | "3" | "4" | "5" | "6" | "7" | "8" | "9" )
{ decimal_digit } .
octal_int_lit = '0' { octal_digit } .
hex_int_lit = '0' ( 'x' | 'X' ) hex_digit { hex_digit } .
float_lit = [ '+' | '-' ] unsigned_float_lit .
octal_int_lit = "0" { octal_digit } .
hex_int_lit = "0" ( "x" | "X" ) hex_digit { hex_digit } .
float_lit = [ "+" | "-" ] unsigned_float_lit .
unsigned_float_lit = "the usual decimal-only floating point representation".
07
@ -389,15 +390,15 @@ Character and string literals are similar to C except:
The rules are:
char_lit = '\'' ( unicode_value | byte_value ) '\'' .
char_lit = "'" ( unicode_value | byte_value ) "'" .
unicode_value = utf8_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 UnicodeValue takes one of four forms:
@ -444,8 +445,8 @@ Double-quoted strings have the usual properties; back-quoted strings
do not interpret backslashes at all.
string_lit = raw_string_lit | interpreted_string_lit .
raw_string_lit = '`' { utf8_char } '`' .
interpreted_string_lit = '"' { unicode_value | byte_value } '"' .
raw_string_lit = "`" { utf8_char } "`" .
interpreted_string_lit = "\"" { unicode_value | byte_value } "\"" .
A string literal has type 'string'. Its value is constructed by
taking the byte values formed by the successive elements of the
@ -532,7 +533,7 @@ Any array may be assigned to an open array variable with the
same element type. Typically, open arrays are used as
formal parameters for functions.
ArrayType = '[' [ ArrayLength ] ']' ElementType .
ArrayType = "[" [ ArrayLength ] "]" ElementType .
ArrayLength = Expression .
ElementType = Type .
@ -553,7 +554,7 @@ Array literals
Array literals represent array constants. All the contained expressions must
be of the same type, which is the element type of the resulting array.
ArrayLit = '[' ExpressionList ']' .
ArrayLit = "[" ExpressionList "]" .
[ 1, 2, 3 ]
[ "x", "y" ]
@ -569,9 +570,9 @@ Upon creation, a map is empty and values may be added and removed
during execution. The number of entries in a map is called its length.
A map whose value type is 'any' can store values of all types.
MapType = 'map' '[' KeyType ']' ValueType .
MapType = "map" "[" KeyType "]" ValueType .
KeyType = Type .
ValueType = Type | 'any' .
ValueType = Type | "any" .
map [string] int
map [struct { pid int; name string }] *chan Buffer
@ -585,9 +586,9 @@ Map literals represent map constants. They comprise a list of (key, value)
pairs. All keys must have the same type; all values must have the same type.
These types define the key and value types for the map.
MapLit = '[' KeyValueList ']' .
KeyValueList = KeyValue { ',' KeyValue } .
KeyValue = Expression ':' Expression .
MapLit = "[" KeyValueList "]" .
KeyValueList = KeyValue { "," KeyValue } .
KeyValue = Expression ":" Expression .
[ "one" : 1, "two" : 2 ]
[ 2: true, 3: true, 5: true, 7: true ]
@ -601,8 +602,8 @@ Struct types are similar to C structs.
Each field of a struct represents a variable within the data
structure.
StructType = 'struct' '{' [ FieldDeclList [ ';' ] ] '}' .
FieldDeclList = FieldDecl { ';' FieldDeclList } .
StructType = "struct" "{" [ FieldDeclList [ ";" ] ] "}" .
FieldDeclList = FieldDecl { ";" FieldDeclList } .
FieldDecl = IdentifierList Type .
// An empty struct.
@ -624,7 +625,7 @@ Struct literals represent struct constants. They comprise a list of
expressions that represent the individual fields of a struct. The
individual expressions must match those of the specified struct type.
StructLit = TypeName '(' [ ExpressionList ] ')' .
StructLit = TypeName "(" [ ExpressionList ] ")" .
The type name must be that of a defined struct type.
@ -637,7 +638,7 @@ Pointer types
Pointer types are similar to those in C.
PointerType = '*' Type.
PointerType = "*" Type.
We do not allow pointer arithmetic of any kind.
@ -659,7 +660,7 @@ Upon creation, a channel can be used both to send and to receive; it
may be restricted only to send or to receive; such a restricted channel
is called a 'send channel' or a 'receive channel'.
ChannelType = 'chan' [ '<' | '>' ] ValueType .
ChannelType = "chan" [ "<" | ">" ] ValueType .
chan any // a generic channel
chan int // a channel that can exchange only ints
@ -681,13 +682,13 @@ A method is a function with a receiver, which is of type pointer to struct.
Functions can return multiple values simultaneously.
FunctionType = 'func' AnonymousSignature .
AnonymousSignature = [ Receiver '.' ] Parameters [ Result ] .
Receiver = '(' identifier Type ')' .
Parameters = '(' [ ParameterList ] ')' .
ParameterList = ParameterSection { ',' ParameterSection } .
FunctionType = "func" AnonymousSignature .
AnonymousSignature = [ Receiver "." ] Parameters [ Result ] .
Receiver = "(" identifier Type ")" .
Parameters = "(" [ ParameterList ] ")" .
ParameterList = ParameterSection { "," ParameterSection } .
ParameterSection = [ IdentifierList ] Type .
Result = Type | '(' ParameterList ')' .
Result = Type | "(" ParameterList ")" .
// Function types
func ()
@ -713,7 +714,7 @@ Function Literals
Function literals represent anonymous functions.
FunctionLit = FunctionType Block .
Block = '{' [ StatementList [ ';' ] ] '}' .
Block = "{" [ StatementList [ ";" ] ] "}" .
The scope of an identifier declared within a block extends
from the declaration of the identifier (that is, the position
@ -773,8 +774,8 @@ Interface types
An interface type denotes a set of methods.
InterfaceType = 'interface' '{' [ MethodDeclList [ ';' ] ] '}' .
MethodDeclList = MethodDecl { ';' MethodDecl } .
InterfaceType = "interface" "{" [ MethodDeclList [ ";" ] ] "}" .
MethodDeclList = MethodDecl { ";" MethodDecl } .
MethodDecl = identifier Parameters [ Result ] .
// A basic file interface.
@ -839,9 +840,9 @@ Const declarations
A constant declaration gives a name to the value of a constant expression.
ConstDecl = 'const' ( ConstSpec | '(' ConstSpecList [ ';' ] ')' ).
ConstSpec = identifier [ Type ] '=' Expression .
ConstSpecList = ConstSpec { ';' ConstSpec }.
ConstDecl = "const" ( ConstSpec | "(" ConstSpecList [ ";" ] ")" ).
ConstSpec = identifier [ Type ] "=" Expression .
ConstSpecList = ConstSpec { ";" ConstSpec }.
const pi float = 3.14159265
const e = 2.718281828
@ -858,9 +859,9 @@ A type declaration introduces a name as a shorthand for a type.
In certain situations, such as conversions, it may be necessary to
use such a type name.
TypeDecl = 'type' ( TypeSpec | '(' TypeSpecList [ ';' ] ')' ).
TypeDecl = "type" ( TypeSpec | "(" TypeSpecList [ ";" ] ")" ).
TypeSpec = identifier Type .
TypeSpecList = TypeSpec { ';' TypeSpec }.
TypeSpecList = TypeSpec { ";" TypeSpec }.
type IntArray [16] int
@ -877,9 +878,9 @@ A variable declaration creates a variable and gives it a type and a name.
It may optionally give the variable an initial value; in some forms of
declaration the type of the initial value defines the type of the variable.
VarDecl = 'var' ( VarSpec | '(' VarSpecList [ ';' ] ')' ) | SimpleVarDecl .
VarSpec = IdentifierList ( Type [ '=' ExpressionList ] | '=' ExpressionList ) .
VarSpecList = VarSpec { ';' VarSpec } .
VarDecl = "var" ( VarSpec | "(" VarSpecList [ ";" ] ")" ) | SimpleVarDecl .
VarSpec = IdentifierList ( Type [ "=" ExpressionList ] | "=" ExpressionList ) .
VarSpecList = VarSpec { ";" VarSpec } .
var i int
var u, v, w float
@ -895,7 +896,7 @@ as there are variables in the variable specification.
The syntax
SimpleVarDecl = identifier ':=' Expression .
SimpleVarDecl = identifier ":=" Expression .
is shorthand for
@ -917,7 +918,7 @@ different from the type syntax because an identifier must be present
in the signature. For now, functions and methods can only be declared
at the global level.
FunctionDecl = 'func' NamedSignature ( ';' | Block ) .
FunctionDecl = "func" NamedSignature ( ";" | Block ) .
NamedSignature = [ Receiver ] identifier Parameters [ Result ] .
func min(x int, y int) int {
@ -972,7 +973,7 @@ source than the export directive itself, but it is an error to specify
an identifier not declared anywhere in the source file containing the
export directive.
ExportDecl = 'export' ExportIdentifier { ',' ExportIdentifier } .
ExportDecl = "export" ExportIdentifier { "," ExportIdentifier } .
ExportIdentifier = QualifiedIdent .
export sin, cos
@ -991,20 +992,20 @@ Expression syntax is based on that of C but with fewer precedence levels.
UnaryExpr = unary_op Expression .
PrimaryExpr =
identifier | Literal | '(' Expression ')' | 'iota' |
identifier | Literal | "(" Expression ")" | "iota" |
Call | Conversion |
Expression '[' Expression [ ':' Expression ] ']' | Expression '.' identifier .
Expression "[" Expression [ ":" Expression ] "]" | Expression "." identifier .
Call = Expression '(' [ ExpressionList ] ')' .
Conversion = TypeName '(' [ ExpressionList ] ')' .
Call = Expression "(" [ ExpressionList ] ")" .
Conversion = TypeName "(" [ ExpressionList ] ")" .
binary_op = log_op | rel_op | add_op | mul_op .
log_op = '||' | '&&' .
rel_op = '==' | '!=' | '<' | '<=' | '>' | '>='.
add_op = '+' | '-' | '|' | '^'.
mul_op = '*' | '/' | '%' | '<<' | '>>' | '&'.
log_op = "||" | "&&" .
rel_op = "==" | "!=" | "<" | "<=" | ">" | ">=".
add_op = "+" | "-" | "|" | "^".
mul_op = "*" | "/" | "%" | "<<" | ">>" | "&".
unary_op = '+' | '-' | '!' | '^' | '<' | '>' | '*' | '&' .
unary_op = "+" | "-" | "!" | "^" | "<" | ">" | "*" | "&" .
Field selection ('.') binds tightest, followed by indexing ('[]') and then calls and conversions.
The remaining precedence levels are as follows (in increasing precedence order):
@ -1132,7 +1133,7 @@ Expression statements
IncDec statements
----
IncDecStat = Expression ( '++' | '--' ) .
IncDecStat = Expression ( "++" | "--" ) .
a[i]++
@ -1146,9 +1147,9 @@ Assignments
SingleAssignment = PrimaryExpr assign_op Expression .
TupleAssignment = PrimaryExprList assign_op ExpressionList .
PrimaryExprList = PrimaryExpr { "," PrimaryExpr } .
Send = '>' Expression '=' Expression .
Send = ">" Expression "=" Expression .
assign_op = [ add_op | mul_op ] '=' .
assign_op = [ add_op | mul_op ] "=" .
The left-hand side must be an l-value such as a variable, pointer indirection,
or an array indexing.
@ -1207,7 +1208,7 @@ concurrent thread of control within the same address space. Unlike
with a function, the next line of the program does not wait for the
function to complete.
GoStat = 'go' Call .
GoStat = "go" Call .
go Server()
@ -1220,7 +1221,7 @@ Return statements
A return statement terminates execution of the containing function
and optionally provides a result value or values to the caller.
ReturnStat = 'return' [ ExpressionList ] .
ReturnStat = "return" [ ExpressionList ] .
There are two ways to return values from a function. The first is to
@ -1259,7 +1260,7 @@ If statements have the traditional form except that the
condition need not be parenthesized and the "then" statement
must be in brace brackets.
IfStat = 'if' [ SimpleVarDecl ';' ] Expression Block [ 'else' Statement ] .
IfStat = "if" [ SimpleVarDecl ";" ] Expression Block [ "else" Statement ] .
if x > 0 {
return true;
@ -1283,10 +1284,10 @@ Switch statements
Switches provide multi-way execution.
SwitchStat = 'switch' [ [ SimpleVarDecl ';' ] [ Expression ] ] '{' { CaseClause } '}' .
CaseClause = CaseList StatementList [ ';' ] [ 'fallthrough' [ ';' ] ] .
SwitchStat = "switch" [ SimpleVarDecl ";" ] [ "Expression ] "{" { CaseClause } "}" .
CaseClause = CaseList StatementList [ ";" ] [ "fallthrough" [ ";" ] ] .
CaseList = Case { Case } .
Case = ( 'case' ExpressionList | 'default' ) ':' .
Case = ( "case" ExpressionList | "default" ) ":" .
There can be at most one default case in a switch statement.
@ -1337,8 +1338,8 @@ For statements
For statements are a combination of the 'for' and 'while' loops of C.
ForStat = 'for' [ Condition | ForClause ] Block .
ForClause = [ InitStat ] ';' [ Condition ] ';' [ PostStat ] .
ForStat = "for" [ Condition | ForClause ] Block .
ForClause = [ InitStat ] ";" [ Condition ] ";" [ PostStat ] .
InitStat = SimpleStat .
Condition = Expression .
@ -1372,7 +1373,7 @@ Range statements
Range statements are a special control structure for iterating over
the contents of arrays and maps.
RangeStat = 'range' IdentifierList ':=' RangeExpression Block .
RangeStat = "range" IdentifierList ":=" RangeExpression Block .
RangeExpression = Expression .
A range expression must evaluate to an array, map or string. The identifier list must contain
@ -1399,7 +1400,7 @@ Break statements
Within a 'for' or 'switch' statement, a 'break' statement terminates execution of
the innermost 'for' or 'switch' statement.
BreakStat = 'break' [ identifier ].
BreakStat = "break" [ identifier ].
If there is an identifier, it must be the label name of an enclosing 'for' or' 'switch'
statement, and that is the one whose execution terminates.
@ -1417,7 +1418,7 @@ Continue statements
Within a 'for' loop a continue statement begins the next iteration of the
loop at the post statement.
ContinueStat = 'continue' [ identifier ].
ContinueStat = "continue" [ identifier ].
The optional identifier is analogous to that of a 'break' statement.
@ -1427,7 +1428,7 @@ Goto statements
A goto statement transfers control to the corresponding label statement.
GotoStat = 'goto' identifier .
GotoStat = "goto" identifier .
goto Error
@ -1437,7 +1438,7 @@ Label declaration
A label declaration serves as the target of a 'goto', 'break' or 'continue' statement.
LabelDecl = identifier ':' .
LabelDecl = identifier ":" .
Error:
@ -1450,7 +1451,7 @@ Packages
Every source file identifies the package to which it belongs.
The file must begin with a package clause.
PackageClause = 'package' PackageName .
PackageClause = "package" PackageName .
package Math
@ -1461,7 +1462,7 @@ Import declarations
A program can gain access to exported items from another package
through an import declaration:
ImportDecl = 'import' [ '.' | PackageName ] PackageFileName .
ImportDecl = "import" [ "." | PackageName ] PackageFileName .
PackageFileName = string_lit .
An import statement makes the exported contents of the named