From: Robert Griesemer <gri@golang.org>
Date: Wed, 3 Sep 2008 20:37:44 +0000 (-0700)
Subject: Composite literal syntax.
X-Git-Tag: weekly.2009-11-06~3286
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=0976e34d654a4020ae00aecae5a0c137a6f23c08;p=gostls13.git

Composite literal syntax.

R=r
DELTA=25  (14 added, 2 deleted, 9 changed)
OCL=14750
CL=14753
---

diff --git a/doc/go_spec.txt b/doc/go_spec.txt
index 574913dba2..4279f23f38 100644
--- a/doc/go_spec.txt
+++ b/doc/go_spec.txt
@@ -4,7 +4,7 @@ The Go Programming Language Specification (DRAFT)
 Robert Griesemer, Rob Pike, Ken Thompson
 
 ----
-(August 29, 2008)
+(September 3, 2008)
 
 
 This document is a semi-formal specification of the Go systems
@@ -438,11 +438,11 @@ The following identifiers are predeclared:
 	
 - the predeclared constants
 
-	true, false, nil
+	true, false, iota, nil
 	
 - the predeclared functions (note: this list is likely to change)
 
-	cap(), convert(), len(), new(), panic(), print(), ...
+	cap(), convert(), len(), new(), panic(), print(), typeof(), ...
 
 
 TODO(gri) We should think hard about reducing the alias type list to:
@@ -1116,16 +1116,23 @@ if omitted, the first two examples above can be abbreviated:
 Composite Literals
 ----
 
-	CompositeLit = ...
-
 Literals for composite data structures consist of the type of the value
-followed by a parenthesized expression list.  In appearance, they are a
-conversion from expression list to composite value.
+followed by a parenthesized expression list for array and structure literals,
+or a list of expression pairs for map literals.
+
+	CompositeLit = LiteralType "(" [ ( ExpressionList | ExprPairList ) [ "," ] ] ")" .
+	LiteralType = TypeName | ArrayType | MapType | StructType .
+	ExprPairList = ExprPair { "," ExprPair } .
+	ExprPair = Expression ":" Expression .
+
+If LiteralType is a TypeName, the denoted type must be an array, map, or
+structure.  The types of the expressions must match the respective key, element,
+and field types of the literal type; there is no automatic type conversion.
 
-Structure literals follow this form directly.  Given
+Given
 
 	type Rat struct { num, den int };
-	type Num struct { r Rat, f float, s string };
+	type Num struct { r Rat; f float; s string };
 
 we can write
 
@@ -1142,12 +1149,17 @@ if a specified size is less than the number of elements in the expression list.
 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: helper syntax for nested arrays etc? (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.
+
+
 Function Literals
 ----