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- incorporated bug fixes, todo's as suggested by rsc

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Robert Griesemer 2008-09-10 13:00:32 -07:00
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53
doc/go_spec.txt
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@ -4,7 +4,7 @@ The Go Programming Language Specification (DRAFT)
Robert Griesemer, Rob Pike, Ken Thompson
----
(September 9, 2008)
(September 10, 2008)
This document is a semi-formal specification of the Go systems
@ -48,6 +48,8 @@ Open issues according to gri:
[ ] need for type switch? (or use type guard with ok in tuple assignment?)
[ ] can we add methods to types defined in another package?
[ ] do we need anything on package vs file names?
[ ] need to talk about precise int/floats clearly
[ ] iant suggests to use abstract/precise int for len(), cap() - good idea
-->
@ -157,6 +159,9 @@ In particular:
Lexical symbols are enclosed in double quotes '''' (the
double quote symbol is written as ''"'').
The form "a ... b" represents the set of characters from "a" through "b" as
alternatives.
A production may be referenced from various places in this document
but is usually defined close to its first use. Productions and code
examples are indented.
@ -199,12 +204,10 @@ to refer to the subset of "utf8_char" code points with values >= 128.
Letters and digits
----
letter = "A" | "a" | ... "Z" | "z" | "_" | non_ascii .
oct_digit = { "0" | "1" | "2" | "3" | "4" | "5" | "6" | "7" } .
dec_digit = { "0" | "1" | "2" | "3" | "4" | "5" | "6" | "7" | "8" | "9" } .
hex_digit =
{ "0" | "1" | "2" | "3" | "4" | "5" | "6" | "7" | "8" | "9" | "a" |
"A" | "b" | "B" | "c" | "C" | "d" | "D" | "e" | "E" | "f" | "F" } .
letter = "A" ... "Z" | "a" ... "z" | "_" | non_ascii.
oct_digit = "0" ... "7" .
dec_digit = "0" ... "9" .
hex_digit = "0" ... "9" | "A" ... "F" | "a" ... "f" .
All non-ASCII code points are considered letters; digits are always ASCII.
@ -412,7 +415,7 @@ The following words are reserved and must not be used as identifiers:
continue for import return var
Declaration and scope rules
Declarations and scope rules
----
Every identifier in a program must be declared; some identifiers, such as "int"
@ -1186,7 +1189,7 @@ Composite Literals
----
Literals for composite data structures consist of the type of the value
followed by a parenthesized expression list for array and structure literals,
followed by a braced expression list for array and structure literals,
or a list of expression pairs for map literals.
CompositeLit = LiteralType "{" [ ( ExpressionList | ExprPairList ) [ "," ] ] "}" .
@ -1431,7 +1434,7 @@ Strings and arrays can be concatenated using the "+" operator
(or via the "+=" assignment):
s := "hi" + string(c)
a += []int(5, 6, 7)
a += []int{5, 6, 7}
String and array addition creates a new array or string by copying the
elements.
@ -1893,7 +1896,7 @@ array elements (the values).
f(a[i]);
}
range v, i := a {
range i, v := a {
f(v);
}
@ -1950,7 +1953,7 @@ which single communication will execute.
var c, c1, c2 *chan int;
select {
case i1 <-c1:
case i1 <- c1:
print("received ", i1, " from c1\n");
case c2 -< i2:
print("sent ", i2, " to c2\n");
@ -2093,13 +2096,14 @@ A function declaration declares an identifier of type function.
}
return y;
}
A function declaration without a body serves as a forward declaration:
func MakeNode(left, right *Node) *Node;
Implementation restriction: Functions can only be declared at the global level.
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
@ -2139,15 +2143,17 @@ Predeclared functions
TODO: (gri) suggests that we should consider assert() as a built-in function.
It is like panic, but takes a guard as first argument.
It is like panic, but takes a boolean guard as first argument. (rsc also thinks
this is a good idea).
Length and capacity
----
The predeclared function "len()" takes a value of array or map type,
or of pointer to array or map type, and returns the number of array
of map elements.
The predeclared function "len()" takes a value of type string,
array or map type, or of pointer to array or map type, and
returns the length of the string in bytes, or the number of array
of map elements, respectively.
The predeclared function "cap()" takes a value of array or pointer
to array type and returns the number of elements for which there
@ -2156,6 +2162,9 @@ following relationship holds:
0 <= len(a) <= cap(a)
TODO(gri) Change this and the following sections to use a table indexed
by functions and parameter types instead of lots of prose.
Conversions
----
@ -2216,14 +2225,14 @@ syntactically like a call to a function whose name is the type:
int(PI * 1000.0);
AStructType(an_interface_variable);
struct{ x int, y float }(3, sqrt(2.0))
[]int(1, 2, 3, 4);
map[string]int("1", 1, "2", 2);
struct{ x int, y float }{3, sqrt(2.0)}
[]int{1, 2, 3, 4};
map[string]int{"1", 1, "2", 2};
This notation is convenient for declaring and initializing
variables of composite type:
primes := []int(2, 3, 5, 7, 9, 11, 13);
primes := []int{2, 3, 5, 7, 9, 11, 13};
Simple conversions can also be written as a parenthesized type after
an expression and a period. Although intended for ease of conversion