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spec: describe slice-to-array conversions

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For #46505.

Change-Id: I1a30fd895496befd16626afb48717ac837ed5778
Reviewed-on: https://go-review.googlesource.com/c/go/+/429315
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Robert Griesemer <gri@google.com>
This commit is contained in:
Robert Griesemer 2022-09-07 14:32:22 -07:00 committed by Robert Griesemer
parent 51c34e2f0b
commit 2c3187cd42
1 changed files with 11 additions and 4 deletions
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15
doc/go_spec.html
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@ -1,6 +1,6 @@
<!--{
"Title": "The Go Programming Language Specification",
"Subtitle": "Version of June 29, 2022",
"Subtitle": "Version of September 8, 2022",
"Path": "/ref/spec"
}-->
@ -5530,16 +5530,23 @@ runes("白鵬翔") // []rune{0x767d, 0x9d6c, 0x7fd4}
</li>
</ol>
<h4 id="Conversions_from_slice_to_array_pointer">Conversions from slice to array pointer</h4>
<h4 id="Conversions_from_slice_to_array_or_array_pointer">Conversions from slice to array or array pointer</h4>
<p>
Converting a slice to an array pointer yields a pointer to the underlying array of the slice.
If the <a href="#Length_and_capacity">length</a> of the slice is less than the length of the array,
Converting a slice to an array yields an array containing the elements of the underlying array of the slice.
Similarly, converting a slice to an array pointer yields a pointer to the underlying array of the slice.
In both cases, if the <a href="#Length_and_capacity">length</a> of the slice is less than the length of the array,
a <a href="#Run_time_panics">run-time panic</a> occurs.
</p>
<pre>
s := make([]byte, 2, 4)
a0 := ([0]byte)(s)
a1 := ([1]byte)(s[1:]) // a1[0] == s[1]
a2 := ([2]byte)(s) // a2[0] == s[0]
a4 := ([4]byte)(s) // panics: len([4]byte) > len(s)
s0 := (*[0]byte)(s) // s0 != nil
s1 := (*[1]byte)(s[1:]) // &amp;s1[0] == &amp;s[1]
s2 := (*[2]byte)(s) // &amp;s2[0] == &amp;s[0]