Proposal for new function type syntax as suggested by ken:
- removed "func" from function type
- make it work by changing composite literal syntax to use {} instead of ()
FunctionType is now more in line with the rest of the declarations, as the
keyword "func" is now really part of the declaration and not part of the type.
R=r,ken
DELTA=49 (14 added, 12 deleted, 23 changed)
OCL=14864
CL=14955
diff --git a/doc/go_spec.txt b/doc/go_spec.txt
index f720249..8caea81 100644
--- a/doc/go_spec.txt
+++ b/doc/go_spec.txt
@@ -4,7 +4,7 @@
Robert Griesemer, Rob Pike, Ken Thompson
----
-(September 4, 2008)
+(September 8, 2008)
This document is a semi-formal specification of the Go systems
@@ -992,22 +992,23 @@
Function types
----
-A function type denotes the set of all functions with the same signature.
+A function type denotes the set of all functions with the same parameter
+list and result.
-Functions can return multiple values simultaneously.
-
- FunctionType = "func" Signature .
- Signature = Parameters [ Result ] .
- Parameters = "(" [ ParameterList ] ")" .
+ FunctionType = "(" [ ParameterList ] ")" [ Result ] .
ParameterList = ParameterSection { "," ParameterSection } .
ParameterSection = IdentifierList Type .
Result = Type | "(" ParameterList ")" .
+Functions can return multiple values simultaneously.
+
// Function types
- func ()
- func (a, b int, z float) bool
- func (a, b int, z float) (success bool)
- func (a, b int, z float) (success bool, result float)
+ ()
+ () int
+ (s string)
+ (a, b int, z float) bool
+ (a, b int, z float) (success bool)
+ (a, b int, z float) (success bool, result float)
A variable can hold only a pointer to a function, not a function value.
In particular, v := func() {} creates a variable of type *func(). To call the
@@ -1025,7 +1026,7 @@
InterfaceType = "interface" "{" [ MethodDeclList [ ";" ] ] "}" .
MethodDeclList = MethodDecl { ";" MethodDecl } .
- MethodDecl = identifier Signature .
+ MethodDecl = identifier FunctionType .
// A basic file interface.
type File interface {
@@ -1125,7 +1126,7 @@
followed by a parenthesized expression list for array and structure literals,
or a list of expression pairs for map literals.
- CompositeLit = LiteralType "(" [ ( ExpressionList | ExprPairList ) [ "," ] ] ")" .
+ CompositeLit = LiteralType "{" [ ( ExpressionList | ExprPairList ) [ "," ] ] "}" .
LiteralType = TypeName | ArrayType | MapType | StructType .
ExprPairList = ExprPair { "," ExprPair } .
ExprPair = Expression ":" Expression .
@@ -1141,7 +1142,7 @@
we can write
- pi := Num(Rat(22,7), 3.14159, "pi")
+ pi := Num{Rat{22, 7}, 3.14159, "pi"};
For array literals, if the length is present the constructed array has that many
elements; trailing elements are given the approprate zero value for that type.
@@ -1150,39 +1151,40 @@
In either case, the length is known at compile type and thus the type of an
array literal is always a fixed array type.
- primes := [6]int(2, 3, 5, 7, 9, 11)
- weekdays := []string("mon", "tue", "wed", "thu", "fri", "sat", "sun")
+ primes := [6]int{2, 3, 5, 7, 9, 11};
+ weekdays := []string{"mon", "tue", "wed", "thu", "fri", "sat", "sun"};
Map literals are similar except the elements of the expression list are
key-value pairs separated by a colon:
- m := map[string]int("good": 0, "bad": 1, "indifferent": 7)
+ m := map[string]int{"good": 0, "bad": 1, "indifferent": 7};
TODO: Consider adding helper syntax for nested composites
(avoids repeating types but complicates the spec needlessly.)
-TODO(gri): These are not conversions and we could use {} instead of () in
-the syntax. This will make literals such as Foo(1, 2, 3) clearly stand
-out from function calls. TBD.
-
-
Function Literals
----
Function literals represent anonymous functions.
- FunctionLit = FunctionType Block .
+ FunctionLit = "func" FunctionType Block .
Block = "{" [ StatementList [ ";" ] ] "}" .
-A function literal can be invoked
-or assigned to a variable of the corresponding function pointer type.
-For now, a function literal can reference only its parameters, global
-variables, and variables declared within the function literal.
+The type of a function literal is a pointer to the function type.
- // Function literal
func (a, b int, z float) bool { return a*b < int(z); }
+A function literal can be assigned to a variable of the
+corresponding function pointer type, or invoked directly.
+
+ f := func(x, y int) int { return x + y; }
+ func(ch *chan int) { ch -< ACK; } (reply_chan)
+
+Implementation restriction: A function literal can reference only
+its parameters, global variables, and variables declared within the
+function literal.
+
Primary expressions
----
@@ -1367,7 +1369,7 @@
String and array addition creates a new array or string by copying the
elements.
-For integer values, / and % satisfy the following relationship:
+For integer values, "/" and "%" satisfy the following relationship:
(a / b) * b + a % b == a
@@ -2016,7 +2018,7 @@
A function declaration declares an identifier of type function.
- FunctionDecl = "func" identifier Signature ( ";" | Block ) .
+ FunctionDecl = "func" identifier FunctionType ( ";" | Block ) .
func min(x int, y int) int {
if x < y {
@@ -2038,7 +2040,7 @@
A method declaration declares a function with a receiver.
- MethodDecl = "func" Receiver identifier Signature ( ";" | Block ) .
+ MethodDecl = "func" Receiver identifier FunctionType ( ";" | Block ) .
Receiver = "(" identifier Type ")" .
A method is bound to the type of its receiver.
@@ -2618,8 +2620,8 @@
Finally, two interface types are equivalent if they both declare the same set of
methods: For each method in the first interface type there is a method in the
-second interface type with the same method name and equivalent signature, and
-vice versa. Note that the declaration order of the methods is not relevant.
+second interface type with the same method name and equivalent function type,
+and vice versa. Note that the declaration order of the methods is not relevant.
[OLD
