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- allow for multiple method names per function type in an interface decl.
- added some initial language with respect to exports R=r DELTA=95 (47 added, 31 deleted, 17 changed) OCL=19407 CL=19426
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Robert Griesemer
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337af31781
110
doc/go_spec.txt
110
doc/go_spec.txt
@ -4,7 +4,7 @@ The Go Programming Language Specification (DRAFT)
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Robert Griesemer, Rob Pike, Ken Thompson
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----
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(November 13, 2008)
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(November 17, 2008)
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This document is a semi-formal specification of the Go systems
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@ -87,6 +87,7 @@ Open issues:
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(require ()'s in control clauses)
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[ ] global var decls: "var a, b, c int = 0, 0, 0" is ok, but "var a, b, c = 0, 0, 0" is not
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(seems inconsistent with "var a = 0", and ":=" notation)
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[ ] const decls: "const a, b = 1, 2" is not allowed - why not? Should be symmetric to vars.
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Decisions in need of integration into the doc:
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@ -142,6 +143,8 @@ Contents
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Reserved words
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Declarations and scope rules
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Predeclared identifiers
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Exported declarations
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Const declarations
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Type declarations
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Variable declarations
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@ -556,7 +559,7 @@ form P surrounded by parentheses:
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List<P> = P { ";" P } [ ";" ] .
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Every identifier in a program must be declared; some identifiers, such as "int"
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and "true", are predeclared.
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and "true", are predeclared (§Predeclared identifiers).
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The ``scope'' of an identifier is the extent of source text within which the
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identifier denotes the bound entity. No identifier may be declared twice in a
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@ -595,51 +598,61 @@ same identifier declared in an outer block.
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An entity is said to be ``local'' to its scope. Declarations in the package
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scope are ``global'' declarations.
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Global declarations optionally may be marked for export with the reserved word
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"export". Local declarations can never be exported.
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Identifiers declared in exported declarations (and no other identifiers)
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are made visible to clients of this package, that is, other packages that import
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this package.
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If the declaration defines a type, the type structure is exported as well. In
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particular, if the declaration defines a new "struct" or "interface" type,
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all structure fields and all structure and interface methods are exported also.
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Predeclared identifiers
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----
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The following identifiers are predeclared:
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All basic types:
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bool, byte, uint8, uint16, uint32, uint64, int8, int16, int32, int64,
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float32, float64, float80, string
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A set of platform-specific convenience types:
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uint, int, float, uintptr
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The predeclared constants:
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true, false, iota, nil
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The predeclared functions (note: this list is likely to change):
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cap(), convert(), len(), new(), panic(), panicln(), print(), println(), typeof(), ...
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Exported declarations
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----
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Global declarations optionally may be marked for ``export'', thus making the
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declared identifier accessible outside the current source file. Another source
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file may then import the package (§Packages) and access exported identifiers
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via qualified identifiers (§Qualified identifiers). Local declarations can
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never be marked for export.
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There are two kinds of exports: If a declaration in a package P is marked with
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the keyword "export", the declared identifier is accessible in any file
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importing P; this is called ``unrestricted export''. If a declaration is
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marked with the keyword "package", the declared identifier is only accessible
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in files belonging to the same package P; this is called ``package-restricted''
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export.
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If the identifier represents a type, it must be a complete type (§Types) and
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the type structure is exported as well. In particular, if the declaration
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defines a "struct" or "interface" type, all structure fields and all structure
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and interface methods are exported also.
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export const pi float = 3.14159265
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export func Parse(source string);
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Note that at the moment the old-style export via ExportDecl is still supported.
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package type Node *struct { val int; next *Node }
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TODO: Eventually we need to be able to restrict visibility of fields and methods.
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(gri) The default should be no struct fields and methods are automatically exported.
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Export should be identifier-based: an identifier is either exported or not, and thus
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visible or not in importing package.
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TODO: Need some text with respect to QualifiedIdents.
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QualifiedIdent = [ PackageName "." ] identifier .
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PackageName = identifier .
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The following identifiers are predeclared:
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- all basic types:
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bool, byte, uint8, uint16, uint32, uint64, int8, int16, int32, int64,
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float32, float64, float80, string
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- a set of platform-specific convenience types:
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uint, int, float, uintptr
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- the predeclared constants:
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true, false, iota, nil
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- the predeclared functions (note: this list is likely to change):
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cap(), convert(), len(), new(), panic(), panicln(), print(), println(), typeof(), ...
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Const declarations
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----
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@ -807,6 +820,10 @@ this construct can be used to declare local temporary variables.
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Export declarations
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----
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TODO:
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1) rephrase this section (much of it covered by Exported declarations)
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2) rethink need for this kind of export
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Global identifiers may be exported, thus making the
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exported identifier visible outside the package. Another package may
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then import the identifier to use it.
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@ -830,10 +847,6 @@ export directive.
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export sin, cos
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export math.abs
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TODO: complete this section
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TODO: export as a mechanism for public and private struct fields?
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Types
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----
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@ -1319,13 +1332,12 @@ An interface type denotes the set of all types that implement at least
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the set of methods specified by the interface type, and the value "nil".
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InterfaceType = "interface" [ "{" [ List<MethodSpec> ] "}" ] .
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MethodSpec = identifier FunctionType .
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MethodSpec = IdentifierList FunctionType .
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// A basic file interface.
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interface {
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Read(b Buffer) bool;
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Write(b Buffer) bool;
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Close();
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Read, Write (b Buffer) bool;
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Close ();
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}
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Any type (including interface types) whose interface has, possibly as a
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@ -1348,8 +1360,7 @@ In general, a type implements an arbitrary number of interfaces.
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For instance, consider the interface
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type Lock interface {
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lock();
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unlock();
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lock, unlock ();
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}
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If S1 and S2 also implement
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@ -1538,7 +1549,12 @@ are known at compile-time.
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Qualified identifiers
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----
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TODO(gri) write this section
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A qualified identifier is an identifier qualified by a package name.
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TODO(gri) expand this section.
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QualifiedIdent = { PackageName "." } identifier .
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PackageName = identifier .
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Iota
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