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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 --> <!-- title The Go Programming Language Specification -->
<!-- subtitle Version of October 25, 2011 --> <!-- subtitle Version of November 1, 2011 -->
<!-- <!--
TODO TODO
@ -1498,12 +1498,10 @@ the body of any nested function.
The following identifiers are implicitly declared in the universe block: The following identifiers are implicitly declared in the universe block:
</p> </p>
<pre class="grammar"> <pre class="grammar">
Basic types: Types:
bool byte complex64 complex128 float32 float64 bool byte complex64 complex128 error float32 float64
int8 int16 int32 int64 rune string uint8 uint16 uint32 uint64 int int8 int16 int32 int64 rune string
uint uint8 uint16 uint32 uint64 uintptr
Architecture-specific convenience types:
int uint uintptr
Constants: Constants:
true false iota true false iota
@ -4323,7 +4321,7 @@ func complex_f3() (re float64, im float64) {
return return
} }
func (devnull) Write(p []byte) (n int, _ os.Error) { func (devnull) Write(p []byte) (n int, _ error) {
n = len(p) n = len(p)
return return
} }
@ -5172,6 +5170,28 @@ the <code>init</code> functions: it will not start the next
the previous one has returned. the previous one has returned.
</p> </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> <h2 id="Run_time_panics">Run-time panics</h2>
<p> <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 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> 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>. with a value of the implementation-defined interface type <code>runtime.Error</code>.
That type defines at least the method That type satisfies the predeclared interface type
<code>String() string</code>. The exact error values that <a href="#Errors"><code>error</code></a>.
represent distinct run-time error conditions are unspecified, The exact error values that
at least for now. represent distinct run-time error conditions are unspecified.
</p> </p>
<pre> <pre>
package runtime package runtime
type Error interface { type Error interface {
String() string error
// and perhaps others // and perhaps other methods
} }
</pre> </pre>