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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
This commit is contained in:
Russ Cox
parent
77567265a8
commit
461dd9126c
250
doc/go_spec.html
250
doc/go_spec.html
@ -551,6 +551,8 @@ defined or a forward declared type (§Forward declarations).
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Most types are always complete; for instance, a pointer
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type is always complete even if it points to an incomplete type
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because the size of the pointer itself is always known.
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(TODO: Need to figure out how forward declarations of
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interface fit in here.)
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</p>
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<p>
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The <i>interface</i> of a type is the set of methods bound to it
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@ -661,6 +663,119 @@ StringLit = string_lit { string_lit } .
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"Alea " /* The die */ `iacta est` /* is cast */ "."
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</pre>
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<h3>Array types</h3>
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<p>
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An array is a numbered sequence of elements of a single
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type, called the element type, which must be complete
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(§Types). The number of elements is called the length and is never
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negative.
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</p>
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<pre class="grammar">
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ArrayType = "[" ArrayLength "]" ElementType .
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ArrayLength = Expression .
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ElementType = CompleteType .
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</pre>
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<p>
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The length is part of the array's type and must must be a constant
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expression (§Constant expressions) that evaluates to a non-negative
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integer value. The length of array <code>a</code> can be discovered
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using the built-in function <code>len(a)</code>, which is a
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compile-time constant. The elements can be indexed by integer
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indices 0 through the <code>len(a)-1</code> (§Indexes).
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</p>
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<pre>
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[32]byte
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[2*N] struct { x, y int32 }
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[1000]*float64
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</pre>
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<h3>Slice types</h3>
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<p>
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A slice is a reference to a contiguous segment of an array and
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contains a numbered sequence of elements from that array. A slice
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type denotes the set of all slices of arrays of its element type.
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A slice value may be <code>nil</code>.
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</p>
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<pre class="grammar">
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SliceType = "[" "]" ElementType .
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</pre>
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<p>
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Like arrays, slices are indexable and have a length. The length of a
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slice <code>s</code> can be discovered by the built-in function
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<code>len(s)</code>; unlike with arrays it may change during
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execution. The elements can be addressed by integer indices 0
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through <code>len(s)-1</code> (§Indexes). The slice index of a
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given element may be less than the index of the same element in the
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underlying array.
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</p>
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<p>
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A slice, once initialized, is always associated with an underlying
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array that holds its elements. A slice therfore shares storage
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with its array and with other slices of the same array; by contrast,
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distinct arrays always represent distinct storage.
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</p>
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<p>
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The array underlying a slice may extend past the end of the slice.
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The <i>capacity</i> is a measure of that extent: it is the sum of
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the length of the slice and the length of the array beyond the slice;
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a slice of length up to that capacity can be created by `slicing' a new
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one from the original slice (§Slices).
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The capacity of a slice <code>a</code> can be discovered using the
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built-in function
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</p>
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<pre>
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cap(s)
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</pre>
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<p>
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and the relationship between <code>len()</code> and <code>cap()</code> is:
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</p>
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<pre>
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0 <= len(a) <= cap(a)
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</pre>
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<p>
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The value of an uninitialized slice is <code>nil</code>.
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The length and capacity of a <code>nil</code> slice
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are 0. A new, initialized slice value for a given element type <code>T</code> is
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made using the built-in function <code>make</code>, which takes a slice type
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and parameters specifying the length and optionally the capacity:
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</p>
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<pre>
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make([]T, length)
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make([]T, length, capacity)
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</pre>
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<p>
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The <code>make()</code> call allocates a new, hidden array to which the returned
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slice value refers. That is, calling <code>make</code>
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</p>
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<pre>
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make([]T, length, capacity)
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</pre>
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<p>
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produces the same slice as allocating an array and slicing it, so these two examples
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result in the same slice:
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</p>
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<pre>
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make([]int, 50, 100)
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new([100]int)[0:50]
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</pre>
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<h3>Struct types</h3>
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<p>
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@ -671,7 +786,7 @@ must be unique and field types must be complete (§Types).
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</p>
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<pre class="grammar">
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StructType = "struct" [ "{" [ FieldDeclList ] "}" ] .
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StructType = "struct" "{" [ FieldDeclList ] "}" .
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FieldDeclList = FieldDecl { ";" FieldDecl } [ ";" ] .
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FieldDecl = (IdentifierList CompleteType | [ "*" ] TypeName) [ Tag ] .
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Tag = StringLit .
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@ -745,36 +860,6 @@ struct {
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}
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</pre>
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<h3>Array types</h3>
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<p>
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An array is a numbered sequence of elements of a single
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type, called the element type, which must be complete
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(§Types). The number of elements is called the length and is never
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negative.
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</p>
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<pre class="grammar">
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ArrayType = "[" ArrayLength "]" ElementType .
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ArrayLength = Expression .
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ElementType = CompleteType .
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</pre>
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<p>
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The length is part of the array's type and must must be a constant
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expression (§Constant expressions) that evaluates to a non-negative
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integer value. The length of array <code>a</code> can be discovered
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using the built-in function <code>len(a)</code>, which is a
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compile-time constant. The elements can be indexed by integer
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indices 0 through the <code>len(a)-1</code> (§Indexes).
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</p>
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<pre>
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[32]byte
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[2*N] struct { x, y int32 }
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[1000]*float64
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</pre>
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<h3>Pointer types</h3>
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<p>
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@ -851,7 +936,7 @@ An interface value may be <code>nil</code>.
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</p>
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<pre class="grammar">
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InterfaceType = "interface" [ "{" [ MethodSpecList ] "}" ] .
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InterfaceType = "interface" "{" [ MethodSpecList ] "}" .
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MethodSpecList = MethodSpec { ";" MethodSpec } [ ";" ] .
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MethodSpec = IdentifierList Signature | InterfaceTypeName .
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InterfaceTypeName = TypeName .
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@ -941,89 +1026,6 @@ type File interface {
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}
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</pre>
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<h3>Slice types</h3>
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<p>
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A slice is a reference to a contiguous segment of an array and
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contains a numbered sequence of elements from that array. A slice
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type denotes the set of all slices of arrays of its element type.
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A slice value may be <code>nil</code>.
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</p>
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<pre class="grammar">
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SliceType = "[" "]" ElementType .
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</pre>
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<p>
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Like arrays, slices are indexable and have a length. The length of a
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slice <code>s</code> can be discovered by the built-in function
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<code>len(s)</code>; unlike with arrays it may change during
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execution. The elements can be addressed by integer indices 0
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through <code>len(s)-1</code> (§Indexes). The slice index of a
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given element may be less than the index of the same element in the
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underlying array.
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</p>
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<p>
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A slice, once initialized, is always associated with an underlying
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array that holds its elements. A slice therfore shares storage
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with its array and with other slices of the same array; by contrast,
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distinct arrays always represent distinct storage.
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</p>
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<p>
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The array underlying a slice may extend past the end of the slice.
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The <i>capacity</i> is a measure of that extent: it is the sum of
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the length of the slice and the length of the array beyond the slice;
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a slice of length up to that capacity can be created by `slicing' a new
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one from the original slice (§Slices).
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The capacity of a slice <code>a</code> can be discovered using the
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built-in function
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</p>
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<pre>
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cap(s)
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</pre>
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<p>
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and the relationship between <code>len()</code> and <code>cap()</code> is:
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</p>
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<pre>
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0 <= len(a) <= cap(a)
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</pre>
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<p>
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The value of an uninitialized slice is <code>nil</code>.
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The length and capacity of a <code>nil</code> slice
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are 0. A new, initialized slice value for a given element type <code>T</code> is
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made using the built-in function <code>make</code>, which takes a slice type
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and parameters specifying the length and optionally the capacity:
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</p>
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<pre>
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make([]T, length)
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make([]T, length, capacity)
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</pre>
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<p>
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The <code>make()</code> call allocates a new, hidden array to which the returned
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slice value refers. That is, calling <code>make</code>
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</p>
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<pre>
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make([]T, length, capacity)
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</pre>
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<p>
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produces the same slice as allocating an array and slicing it, so these two examples
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result in the same slice:
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</p>
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<pre>
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make([]int, 50, 100)
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new([100]int)[0:50]
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</pre>
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<h3>Map types</h3>
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<p>
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@ -1208,20 +1210,24 @@ type (
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</pre>
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<p>
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these types are equal
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these types are equal:
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</p>
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<pre>
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T0 and T0
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T0 and T1
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T0 and []string
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T2 and T3
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T4 and T5
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T3 and struct { a int; int }
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T3 and struct { a int; c int }
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</pre>
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<p>
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and these types are identical
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<code>T2</code> and <code>T3</code> are not equal because
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they have different field names.
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</p>
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<p>
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These types are identical:
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</p>
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<pre>
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@ -1548,7 +1554,7 @@ to a new type. <font color=red>TODO: what exactly is a "new type"?</font>
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<pre class="grammar">
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TypeDecl = "type" ( TypeSpec | "(" [ TypeSpecList ] ")" ) .
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TypeSpecList = TypeSpec { ";" TypeSpec } [ ";" ] .
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TypeSpec = identifier Type .
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TypeSpec = identifier ( Type | "struct" | "interface" ) .
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</pre>
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<pre>
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@ -1559,9 +1565,11 @@ type (
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Polar Point
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)
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type Comparable interface
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type TreeNode struct {
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left, right *TreeNode;
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value Point;
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value *Comparable;
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}
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type Comparable interface {
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