diff --git a/doc/go_spec.html b/doc/go_spec.html index 910f8651fa1..9498c4cf984 100644 --- a/doc/go_spec.html +++ b/doc/go_spec.html @@ -167,7 +167,7 @@ _x9 ThisVariableIsExported αβ -Some identifiers are predeclared (§Predeclared identifiers). +Some identifiers are predeclared.
A struct is a sequence of named elements, called fields, with various types. A struct type declares -an identifier and type for each field. Within a struct, field identifiers -must be unique. +an identifier and type for each field. Within a struct, non-blank +field identifiers must be unique.
@@ -680,10 +680,11 @@ Tag = StringLit . // An empty struct. struct {} -// A struct with 5 fields. +// A struct with 6 fields. struct { x, y int; u float; + _ float; // padding A *[]int; F func(); } @@ -1168,6 +1169,9 @@ A bidirectional channelc
can be assigned to a channel variablev
with compatible channel value type if the type ofc
orv
is unnamed. +
-Blocks nest and influence scoping (§Declarations and scope). +Blocks nest and influence scoping.
-A declaration binds an identifier to a constant, type, variable, function, or package. +A declaration binds a non-blank +identifier to a constant, type, variable, function, or package. Every identifier in a program must be declared. No identifier may be declared twice in the same block, and no identifier may be declared in both the file and package block. @@ -1372,6 +1377,14 @@ All other identifiers are not exported.
+
+The blank identifier, represented by the underscore character _
, may be used in a declaration like
+any other identifier but the declaration does not introduce a new binding.
+
@@ -1449,7 +1462,7 @@ set of related constants:
-const ( // iota is reset to 0 +const ( // iota is reset to 0 c0 = iota; // c0 == 0 c1 = iota; // c1 == 1 c2 = iota // c2 == 2 @@ -1480,7 +1493,8 @@ it is only incremented at a semicolon: const ( bit0, mask0 = 1 << iota, 1 << iota - 1; // bit0 == 1, mask0 == 0 bit1, mask1; // bit1 == 2, mask1 == 1 - bit2, mask2; // bit2 == 4, mask2 == 3 + _, _; // skips iota == 2 + bit3, mask3; // bit3 == 8, mask3 == 7 )@@ -1542,6 +1556,8 @@ var ( i int; u, v, s = 2.0, 3.0, "bar" ) +var re, im = complexSqrt(-1) +var _, found = entries[name]; // map lookup; only interested in "found"
@@ -1589,12 +1605,13 @@ i, j := 0, 10; f := func() int { return 7; } ch := make(chan int); r, w := os.Pipe(fd); // os.Pipe() returns two values +_, y, _ := coord(p); // coord() returns three values; only interested in y "projection"
Unlike regular variable declarations, a short variable declaration may redeclare variables provided they were originally declared in the same block with the same type, and at -least one of the variables is new. As a consequence, redeclaration +least one of the non-blank variables is new. As a consequence, redeclaration can only appear in a multi-variable short declaration. Redeclaration does not introduce a new variable; it just assigns a new value to the original. @@ -1734,12 +1751,11 @@ Constants have values that are known at compile time.
-A qualified identifier is an identifier qualified by a package name prefix. +A qualified identifier is a non-blank identifier qualified by a package name prefix.
QualifiedIdent = [ PackageName "." ] identifier . -PackageName = identifier .
@@ -1752,6 +1768,10 @@ package, which means that it must begin with a Unicode upper case letter. Math.Sin +
+TODO: Unify this section with Selectors - it's the same syntax. +
+
@@ -1998,7 +2018,7 @@ denotes the field or method f
of the value denoted by x
*x if
x
is of pointer type). The identifier f
is called the (field or method)
-selector.
+selector; it must not be the blank identifier.
The type of the expression is the type of f
.
@@ -3096,7 +3116,7 @@ assign_op = [ add_op | mul_op ] "=" .
Each left-hand side operand must be a variable, pointer indirection, -field selector, or index expression. +field selector, index expression, or blank identifier.
@@ -3126,7 +3146,7 @@ first, the right hand operand is a single multi-valued expression such as a function evaluation or channel or map operation or a type assertion. The number of operands on the left -hand side must match the number of values. For instance, If +hand side must match the number of values. For instance, iff
is a function returning two values, @@ -3136,8 +3156,14 @@ x, y = f()assigns the first value to
+x
and the second toy
. +The blank identifier provides a convenient +way to ignore values returned by a multi-valued expression:+x, _ = f() // ignore second value returned by f() ++In the second form, the number of operands on the left must equal the number of expressions on the right, each of which must be single-valued, and the @@ -3998,7 +4024,7 @@ m := make(map[string] int, 100); # map with initial space for 100 elements Go programs are constructed by linking together packages. A package is in turn constructed from one or more source files that together provide access to a set of types, constants, functions, -and variables. Those elements may be imported and used in +and variables. Those elements may be exported and used in another package.
@@ -4024,9 +4050,14 @@ to which the file belongs.-PackageClause = "package" PackageName . +PackageClause = "package" PackageName . +PackageName = identifier .++The PackageName must not be the blank identifier. +
+package math