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spec: add error

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R=golang-dev, dsymonds, r, r
CC=golang-dev
https://golang.org/cl/5308072
This commit is contained in:
Russ Cox 2011-11-01 21:45:02 -04:00
parent 9a0563548b
commit d9877e22fe
1 changed files with 34 additions and 14 deletions
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48
doc/go_spec.html
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@ -1,5 +1,5 @@
<!-- title The Go Programming Language Specification -->
<!-- subtitle Version of October 25, 2011 -->
<!-- subtitle Version of November 1, 2011 -->
<!--
TODO
@ -1498,12 +1498,10 @@ the body of any nested function.
The following identifiers are implicitly declared in the universe block:
</p>
<pre class="grammar">
Basic types:
bool byte complex64 complex128 float32 float64
int8 int16 int32 int64 rune string uint8 uint16 uint32 uint64
Architecture-specific convenience types:
int uint uintptr
Types:
bool byte complex64 complex128 error float32 float64
int int8 int16 int32 int64 rune string
uint uint8 uint16 uint32 uint64 uintptr
Constants:
true false iota
@ -4323,7 +4321,7 @@ func complex_f3() (re float64, im float64) {
return
}
func (devnull) Write(p []byte) (n int, _ os.Error) {
func (devnull) Write(p []byte) (n int, _ error) {
n = len(p)
return
}
@ -5172,6 +5170,28 @@ the <code>init</code> functions: it will not start the next
the previous one has returned.
</p>
<h2 id="Errors">Errors</h2>
<p>
The predeclared type <code>error</code> is defined as
</p>
<pre>
type error interface {
Error() string
}
</pre>
<p>
It is the conventional interface for representing an error condition,
with the nil value representing no error.
For instance, a function to read data from a file might be defined:
</p>
<pre>
func Read(f *File, b []byte) (n int, err error)
</pre>
<h2 id="Run_time_panics">Run-time panics</h2>
<p>
@ -5179,18 +5199,18 @@ Execution errors such as attempting to index an array out
of bounds trigger a <i>run-time panic</i> equivalent to a call of
the built-in function <a href="#Handling_panics"><code>panic</code></a>
with a value of the implementation-defined interface type <code>runtime.Error</code>.
That type defines at least the method
<code>String() string</code>. The exact error values that
represent distinct run-time error conditions are unspecified,
at least for now.
That type satisfies the predeclared interface type
<a href="#Errors"><code>error</code></a>.
The exact error values that
represent distinct run-time error conditions are unspecified.
</p>
<pre>
package runtime
type Error interface {
String() string
// and perhaps others
error
// and perhaps other methods
}
</pre>