Commit 1f3e842c authored by Robert Griesemer's avatar Robert Griesemer

Some initial language towards embedded types and methods for all types.

More to come.

R=r
DELTA=74  (47 added, 8 deleted, 19 changed)
OCL=16156
CL=16159
parent aadd3222
......@@ -52,11 +52,14 @@ Open issues according to gri:
[ ] type switch or some form of type test needed
[ ] what is the meaning of typeof()
[ ] at the moment: type T S; strips any methods of S. It probably shouldn't.
[ ] talk about underflow/overflow of 2's complement numbers (defined vs not defined).
[ ] 6g allows: interface { f F } where F is a function type. fine, but then we should
also allow: func f F {}, where F is a function type.
Decisions in need of integration into the doc:
[ ] pair assignment is required to get map, and receive ok.
[ ] change wording on array composite literals: the types are always fixed arrays
for array composites
Closed issues:
[x] remove "any"
......@@ -64,7 +67,6 @@ Closed issues:
[x] should binary <- be at lowest precedence level? when is a send/receive non-blocking? (NO - 9/19/08)
[x] func literal like a composite type - should probably require the '&' to get address (NO)
[x] & needed to get a function pointer from a function? (NO - there is the "func" keyword - 9/19/08)
-->
Contents
......@@ -77,7 +79,7 @@ Contents
Source code representation
Characters
Letters and digits
Vocabulary
Identifiers
Numeric literals
......@@ -92,11 +94,13 @@ Contents
Export declarations
Types
Type interfaces
Basic types
Arithmetic types
Booleans
Strings
Array types
Struct types
Pointer types
......@@ -119,14 +123,14 @@ Contents
Slices
Type guards
Calls
Operators
Arithmetic operators
Comparison operators
Logical operators
Address operators
Communication operators
Constant expressions
Statements
......@@ -147,11 +151,11 @@ Contents
Goto statements
Function declarations
Methods (type-bound functions)
Predeclared functions
Length and capacity
Conversions
Allocation
Method declarations
Predeclared functions
Length and capacity
Conversions
Allocation
Packages
......@@ -754,6 +758,11 @@ with the static type of the variable.
TypeName = QualifiedIdent.
Type interfaces
----
TODO fill in this section
Basic types
----
......@@ -983,9 +992,6 @@ to arrays and arrays.
Struct types
----
TODO: The language below needs to be adjusted for inlined types. The syntax
is probably all right.
A struct is a composite type consisting of a fixed number of elements,
called fields, with possibly different types. The struct type declaration
specifies the name and type for each field. The scope of each field identifier
......@@ -995,10 +1001,6 @@ it is also visible within field selectors (§Primary Expressions).
StructType = "struct" "{" [ FieldList [ ";" ] ] "}" .
FieldList = FieldDecl { ";" FieldDecl } .
FieldDecl = [ IdentifierList ] Type .
Type equality: Two struct types are equal only if both have the same number
of fields in the same order and and the field types are equal
(note that the field names do not have to match).
// An empty struct.
struct {}
......@@ -1010,7 +1012,31 @@ of fields in the same order and and the field types are equal
a *[]int;
f *();
}
A struct may contain ``embedded types''. An embedded type is declared with
a type name but no explicit field name. Instead, the type name acts as the
field name.
// A struct with a single embedded type T.
struct {
x, y int;
T;
}
As with all scopes, each field name must be unique within a single struct
(§Declarations and scope rules); consequently, the name of an embedded type
must not conflict with the name of any other field or embedded type within
the scope of the struct.
Fields and methods (§Method declarations) of an embedded type become directly
accessible as fields and methods of the struct without the need to specify the
embedded type (§TODO).
Type equality: Two struct types are equal only if both have the same number
of fields in the same order, corresponding fields are either both embedded
types or they are not, and the corresponding field types are equal.
Specifically, field names don't have to match.
Assignment compatibility: Structs are assignment compatible to variables of
equal type only.
......@@ -1156,11 +1182,12 @@ Assignment compatibility: A function pointer can be assigned to a function
Interface types
----
An interface type denotes a set of methods.
An interface type denotes the set of all types that implement the
set of methods specified by the interface type.
InterfaceType = "interface" "{" [ MethodList [ ";" ] ] "}" .
MethodList = Method { ";" Method } .
Method = identifier FunctionType .
MethodList = MethodSpec { ";" MethodSpec } .
MethodSpec = identifier FunctionType .
// A basic file interface.
type File interface {
......@@ -2246,15 +2273,25 @@ Implementation restrictions: Functions can only be declared at the global level.
A function must be declared or forward-declared before it can be invoked.
Methods
Method declarations
----
A method declaration declares a function with a receiver.
A method declaration is a function declaration with a receiver. The receiver
is the first parameter of the method, and the receiver type must be specified
as a type name, or as a pointer to a type name. The type specified by the
type name is called ``receiver base type''. The receiver base type must be a
type declared in the current file. The method is said to be ``bound'' to
the receiver base type; specifically it is declared within the scope of
that type (§Type interfaces).
MethodDecl = "func" Receiver identifier FunctionType ( ";" | Block ) .
Receiver = "(" identifier Type ")" .
Receiver = "(" identifier [ "*" ] TypeName ")" .
All methods bound to a receiver base type must have the same receiver type:
Either all receiver types are pointers to the base type or they are the base
type. (TODO: This restriction can be relaxed at the cost of more complicated
assignment rules to interface types).
A method is bound to the type of its receiver.
For instance, given type Point, the declarations
func (p *Point) Length() float {
......@@ -2266,8 +2303,10 @@ For instance, given type Point, the declarations
p.y = p.y * factor;
}
create methods for type *Point. Note that methods may appear anywhere
after the declaration of the receiver type and may be forward-declared.
bind the methods "Length" and "Scale" to the receiver base type "Point".
Method declarations may appear anywhere after the declaration of the receiver
base type and may be forward-declared.
Predeclared functions
......
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