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Commit 461dd912 authored by Russ Cox's avatar Russ Cox
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change Go logo to link to home page 

fix grammar for forward declaration of interface, struct.

move array down next to slice.

fix type equal example for structs.

R=r,gri
DELTA=247  (122 added, 114 deleted, 11 changed)
OCL=25694
CL=25704
parent 77567265
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doc/go_spec.html
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......@@ -551,6 +551,8 @@ defined or a forward declared type (§Forward declarations).
Most types are always complete; for instance, a pointer
type is always complete even if it points to an incomplete type
because the size of the pointer itself is always known.
(TODO: Need to figure out how forward declarations of
interface fit in here.)
</p>
<p>
The <i>interface</i> of a type is the set of methods bound to it
......@@ -661,6 +663,119 @@ StringLit = string_lit { string_lit } .
"Alea " /* The die */ `iacta est` /* is cast */ "."
</pre>
<h3>Array types</h3>
<p>
An array is a numbered sequence of elements of a single
type, called the element type, which must be complete
(§Types). The number of elements is called the length and is never
negative.
</p>
<pre class="grammar">
ArrayType = "[" ArrayLength "]" ElementType .
ArrayLength = Expression .
ElementType = CompleteType .
</pre>
<p>
The length is part of the array's type and must must be a constant
expression (§Constant expressions) that evaluates to a non-negative
integer value. The length of array <code>a</code> can be discovered
using the built-in function <code>len(a)</code>, which is a
compile-time constant. The elements can be indexed by integer
indices 0 through the <code>len(a)-1</code> (§Indexes).
</p>
<pre>
[32]byte
[2*N] struct { x, y int32 }
[1000]*float64
</pre>
<h3>Slice types</h3>
<p>
A slice is a reference to a contiguous segment of an array and
contains a numbered sequence of elements from that array. A slice
type denotes the set of all slices of arrays of its element type.
A slice value may be <code>nil</code>.
</p>
<pre class="grammar">
SliceType = "[" "]" ElementType .
</pre>
<p>
Like arrays, slices are indexable and have a length. The length of a
slice <code>s</code> can be discovered by the built-in function
<code>len(s)</code>; unlike with arrays it may change during
execution. The elements can be addressed by integer indices 0
through <code>len(s)-1</code> (§Indexes). The slice index of a
given element may be less than the index of the same element in the
underlying array.
</p>
<p>
A slice, once initialized, is always associated with an underlying
array that holds its elements. A slice therfore shares storage
with its array and with other slices of the same array; by contrast,
distinct arrays always represent distinct storage.
</p>
<p>
The array underlying a slice may extend past the end of the slice.
The <i>capacity</i> is a measure of that extent: it is the sum of
the length of the slice and the length of the array beyond the slice;
a slice of length up to that capacity can be created by `slicing' a new
one from the original slice (§Slices).
The capacity of a slice <code>a</code> can be discovered using the
built-in function
</p>
<pre>
cap(s)
</pre>
<p>
and the relationship between <code>len()</code> and <code>cap()</code> is:
</p>
<pre>
0 <= len(a) <= cap(a)
</pre>
<p>
The value of an uninitialized slice is <code>nil</code>.
The length and capacity of a <code>nil</code> slice
are 0. A new, initialized slice value for a given element type <code>T</code> is
made using the built-in function <code>make</code>, which takes a slice type
and parameters specifying the length and optionally the capacity:
</p>
<pre>
make([]T, length)
make([]T, length, capacity)
</pre>
<p>
The <code>make()</code> call allocates a new, hidden array to which the returned
slice value refers. That is, calling <code>make</code>
</p>
<pre>
make([]T, length, capacity)
</pre>
<p>
produces the same slice as allocating an array and slicing it, so these two examples
result in the same slice:
</p>
<pre>
make([]int, 50, 100)
new([100]int)[0:50]
</pre>
<h3>Struct types</h3>
<p>
......@@ -671,7 +786,7 @@ must be unique and field types must be complete (§Types).
</p>
<pre class="grammar">
StructType = "struct" [ "{" [ FieldDeclList ] "}" ] .
StructType = "struct" "{" [ FieldDeclList ] "}" .
FieldDeclList = FieldDecl { ";" FieldDecl } [ ";" ] .
FieldDecl = (IdentifierList CompleteType | [ "*" ] TypeName) [ Tag ] .
Tag = StringLit .
......@@ -745,36 +860,6 @@ struct {
}
</pre>
<h3>Array types</h3>
<p>
An array is a numbered sequence of elements of a single
type, called the element type, which must be complete
(§Types). The number of elements is called the length and is never
negative.
</p>
<pre class="grammar">
ArrayType = "[" ArrayLength "]" ElementType .
ArrayLength = Expression .
ElementType = CompleteType .
</pre>
<p>
The length is part of the array's type and must must be a constant
expression (§Constant expressions) that evaluates to a non-negative
integer value. The length of array <code>a</code> can be discovered
using the built-in function <code>len(a)</code>, which is a
compile-time constant. The elements can be indexed by integer
indices 0 through the <code>len(a)-1</code> (§Indexes).
</p>
<pre>
[32]byte
[2*N] struct { x, y int32 }
[1000]*float64
</pre>
<h3>Pointer types</h3>
<p>
......@@ -851,7 +936,7 @@ An interface value may be <code>nil</code>.
</p>
<pre class="grammar">
InterfaceType = "interface" [ "{" [ MethodSpecList ] "}" ] .
InterfaceType = "interface" "{" [ MethodSpecList ] "}" .
MethodSpecList = MethodSpec { ";" MethodSpec } [ ";" ] .
MethodSpec = IdentifierList Signature | InterfaceTypeName .
InterfaceTypeName = TypeName .
......@@ -941,89 +1026,6 @@ type File interface {
}
</pre>
<h3>Slice types</h3>
<p>
A slice is a reference to a contiguous segment of an array and
contains a numbered sequence of elements from that array. A slice
type denotes the set of all slices of arrays of its element type.
A slice value may be <code>nil</code>.
</p>
<pre class="grammar">
SliceType = "[" "]" ElementType .
</pre>
<p>
Like arrays, slices are indexable and have a length. The length of a
slice <code>s</code> can be discovered by the built-in function
<code>len(s)</code>; unlike with arrays it may change during
execution. The elements can be addressed by integer indices 0
through <code>len(s)-1</code> (§Indexes). The slice index of a
given element may be less than the index of the same element in the
underlying array.
</p>
<p>
A slice, once initialized, is always associated with an underlying
array that holds its elements. A slice therfore shares storage
with its array and with other slices of the same array; by contrast,
distinct arrays always represent distinct storage.
</p>
<p>
The array underlying a slice may extend past the end of the slice.
The <i>capacity</i> is a measure of that extent: it is the sum of
the length of the slice and the length of the array beyond the slice;
a slice of length up to that capacity can be created by `slicing' a new
one from the original slice (§Slices).
The capacity of a slice <code>a</code> can be discovered using the
built-in function
</p>
<pre>
cap(s)
</pre>
<p>
and the relationship between <code>len()</code> and <code>cap()</code> is:
</p>
<pre>
0 <= len(a) <= cap(a)
</pre>
<p>
The value of an uninitialized slice is <code>nil</code>.
The length and capacity of a <code>nil</code> slice
are 0. A new, initialized slice value for a given element type <code>T</code> is
made using the built-in function <code>make</code>, which takes a slice type
and parameters specifying the length and optionally the capacity:
</p>
<pre>
make([]T, length)
make([]T, length, capacity)
</pre>
<p>
The <code>make()</code> call allocates a new, hidden array to which the returned
slice value refers. That is, calling <code>make</code>
</p>
<pre>
make([]T, length, capacity)
</pre>
<p>
produces the same slice as allocating an array and slicing it, so these two examples
result in the same slice:
</p>
<pre>
make([]int, 50, 100)
new([100]int)[0:50]
</pre>
<h3>Map types</h3>
<p>
......@@ -1208,20 +1210,24 @@ type (
</pre>
<p>
these types are equal
these types are equal:
</p>
<pre>
T0 and T0
T0 and T1
T0 and []string
T2 and T3
T4 and T5
T3 and struct { a int; int }
T3 and struct { a int; c int }
</pre>
<p>
and these types are identical
<code>T2</code> and <code>T3</code> are not equal because
they have different field names.
</p>
<p>
These types are identical:
</p>
<pre>
......@@ -1548,7 +1554,7 @@ to a new type. <font color=red>TODO: what exactly is a "new type"?</font>
<pre class="grammar">
TypeDecl = "type" ( TypeSpec | "(" [ TypeSpecList ] ")" ) .
TypeSpecList = TypeSpec { ";" TypeSpec } [ ";" ] .
TypeSpec = identifier Type .
TypeSpec = identifier ( Type | "struct" | "interface" ) .
</pre>
<pre>
......@@ -1559,9 +1565,11 @@ type (
Polar Point
)
type Comparable interface
type TreeNode struct {
left, right *TreeNode;
value Point;
value *Comparable;
}
type Comparable interface {
......
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