mirror of
https://github.com/golang/go
synced 2024-11-11 22:50:22 -07:00
add simple text about & and *.
clean up html: PLEASE RUN TIDY WHEN YOU EDIT THIS DOCUMENT deferring method value update until we decide what happens. R=gri DELTA=50 (38 added, 4 deleted, 8 changed) OCL=26609 CL=26612
This commit is contained in:
parent
808341dd6e
commit
afee1c5f0c
@ -22,7 +22,6 @@ Todo's:
|
||||
[ ] need to talk about precise int/floats clearly
|
||||
[ ] iant suggests to use abstract/precise int for len(), cap() - good idea
|
||||
(issue: what happens in len() + const - what is the type?)
|
||||
[ ] cleanup convert() vs T() vs x.(T) - convert() should go away?
|
||||
[ ] fix "else" part of if statement
|
||||
[ ] cleanup: 6g allows: interface { f F } where F is a function type.
|
||||
fine, but then we should also allow: func f F {}, where F is a function type.
|
||||
@ -124,6 +123,7 @@ Closed:
|
||||
and if so, does a label followed by an empty statement (a semicolon) still denote
|
||||
a for loop that is following, and can break L be used inside it?
|
||||
[x] there is some funniness regarding ';' and empty statements and label decls
|
||||
[x] cleanup convert() vs T() vs x.(T) - convert() should go away?
|
||||
|
||||
-->
|
||||
|
||||
@ -1403,7 +1403,6 @@ Constants:
|
||||
|
||||
Functions:
|
||||
cap len make new panic panicln print println
|
||||
(TODO: typeof??)
|
||||
|
||||
Packages:
|
||||
sys (TODO: does sys endure?)
|
||||
@ -2664,17 +2663,30 @@ The right operand is evaluated conditionally.
|
||||
|
||||
<h3>Address operators</h3>
|
||||
|
||||
<!--TODO(r): This section is a mess. Skipping it for now.-->
|
||||
|
||||
<p>
|
||||
<font color=red>TODO: Need to talk about unary "*", clean up section below.</font>
|
||||
The unary prefix address-of operator <code>&</code> generates the address of its operand, which must be a variable,
|
||||
pointer indirection, field selector, or array or slice indexing operation. It is illegal to take the address of a function
|
||||
result variable.
|
||||
Given an operand of pointer type, the unary prefix pointer indirection operator <code>*</code> retrieves the value pointed
|
||||
to by the operand.
|
||||
</p>
|
||||
|
||||
<pre>
|
||||
&x
|
||||
&a[f(2)]
|
||||
*p
|
||||
*pf(x)
|
||||
</pre>
|
||||
|
||||
<p>
|
||||
<font color=red>TODO: This text needs to be cleaned up and go elsewhere, there are no address
|
||||
operators involved.
|
||||
</font>
|
||||
</p>
|
||||
<p>
|
||||
Methods are a form of function, and a method ``value'' has a function type.
|
||||
Methods are a form of function and a method ``value'' has a function type.
|
||||
Consider the type T with method M:
|
||||
</p>
|
||||
|
||||
<pre>
|
||||
type T struct {
|
||||
@ -2684,25 +2696,33 @@ func (tp *T) M(a int) int;
|
||||
var t *T;
|
||||
</pre>
|
||||
|
||||
<p>
|
||||
To construct the value of method M, one writes
|
||||
</p>
|
||||
|
||||
<pre>
|
||||
t.M
|
||||
</pre>
|
||||
|
||||
<p>
|
||||
using the variable t (not the type T).
|
||||
<font color=red>TODO: It makes perfect sense to be able to say T.M (in fact, it makes more
|
||||
sense then t.M, since only the type T is needed to find the method M, i.e.,
|
||||
its address). TBD.
|
||||
</font>
|
||||
</p>
|
||||
|
||||
<p>
|
||||
The expression t.M is a function value with type
|
||||
</p>
|
||||
|
||||
<pre>
|
||||
func (t *T, a int) int
|
||||
</pre>
|
||||
|
||||
<p>
|
||||
and may be invoked only as a function, not as a method:
|
||||
</p>
|
||||
|
||||
<pre>
|
||||
var f func (t *T, a int) int;
|
||||
@ -2710,30 +2730,39 @@ f = t.M;
|
||||
x := f(t, 7);
|
||||
</pre>
|
||||
|
||||
<p>
|
||||
Note that one does not write t.f(7); taking the value of a method demotes
|
||||
it to a function.
|
||||
</p>
|
||||
|
||||
<p>
|
||||
In general, given type T with method M and variable t of type T,
|
||||
the method invocation
|
||||
</p>
|
||||
|
||||
<pre>
|
||||
t.M(args)
|
||||
</pre>
|
||||
|
||||
<p>
|
||||
is equivalent to the function call
|
||||
</p>
|
||||
|
||||
<pre>
|
||||
(t.M)(t, args)
|
||||
</pre>
|
||||
|
||||
<p>
|
||||
<font color=red>
|
||||
TODO: should probably describe the effect of (t.m) under §Expressions if t.m
|
||||
denotes a method: Effect is as described above, converts into function.
|
||||
</font>
|
||||
</p>
|
||||
<p>
|
||||
If T is an interface type, the expression t.M does not determine which
|
||||
underlying type's M is called until the point of the call itself. Thus given
|
||||
T1 and T2, both implementing interface I with method M, the sequence
|
||||
</p>
|
||||
|
||||
<pre>
|
||||
var t1 *T1;
|
||||
@ -2743,8 +2772,10 @@ m := i.M;
|
||||
m(t2, 7);
|
||||
</pre>
|
||||
|
||||
<p>
|
||||
will invoke t2.M() even though m was constructed with an expression involving
|
||||
t1. Effectively, the value of m is a function literal
|
||||
</p>
|
||||
|
||||
<pre>
|
||||
func (recv I, a int) {
|
||||
@ -2752,13 +2783,16 @@ func (recv I, a int) {
|
||||
}
|
||||
</pre>
|
||||
|
||||
<p>
|
||||
that is automatically created.
|
||||
</p>
|
||||
<p>
|
||||
<font color=red>
|
||||
TODO: Document implementation restriction: It is illegal to take the address
|
||||
of a result parameter (e.g.: func f() (x int, p *int) { return 2, &x }).
|
||||
(TBD: is it an implementation restriction or fact?)
|
||||
</font>
|
||||
</p>
|
||||
|
||||
<h3>Communication operators</h3>
|
||||
|
||||
@ -3131,11 +3165,13 @@ if x := f(); x < y {
|
||||
An expression or type specifier is compared to the "cases"
|
||||
inside the "switch" to determine which branch
|
||||
to execute.
|
||||
</p>
|
||||
|
||||
<pre class="grammar">
|
||||
SwitchStat = ExprSwitchStat | TypeSwitchStat .
|
||||
</pre>
|
||||
|
||||
<p>
|
||||
There are two forms: expression switches and type switches.
|
||||
In an expression switch, the cases contain expressions that are compared
|
||||
against the value of the switch expression.
|
||||
@ -3690,7 +3726,6 @@ for i := 0; i <= 3; i++ {
|
||||
<h2>Predeclared functions</h2>
|
||||
<ul>
|
||||
<li>cap
|
||||
<li>convert
|
||||
<li>len
|
||||
<li>make
|
||||
<li>new
|
||||
@ -3698,7 +3733,6 @@ for i := 0; i <= 3; i++ {
|
||||
<li>panicln
|
||||
<li>print
|
||||
<li>println
|
||||
<li>typeof
|
||||
</ul>
|
||||
|
||||
<h3>Length and capacity</h3>
|
||||
|
Loading…
Reference in New Issue
Block a user