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spec for range on strings

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Rob Pike 2009-04-15 20:28:25 -07:00
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commit 7aee71bd4f
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doc/go_spec.html
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@ -3444,7 +3444,8 @@ for true { S() } is the same as for { S() }
<p>
A "for" statement with a "range" clause
iterates through all entries of an array, slice or map.
iterates through all entries of an array, slice, string or map,
or values received on a channel.
For each entry it first assigns the current index or key to an iteration
variable - or the current (index, element) or (key, value) pair to a pair
of iteration variables - and then executes the block.
@ -3455,20 +3456,30 @@ RangeClause = IdentifierList ( "=" | ":=" ) "range" Expression .
</pre>
<p>
The type of the right-hand expression in the "range" clause must be an array,
slice or map, or a pointer to an array, slice or map;
The type of the right-hand expression in the "range" clause must be an
array, slice, string or map, or a pointer to an array, slice, string or map;
or it may be a channel.
If it is an array, slice or map,
Except for channels,
the identifier list must contain one or two identifiers denoting the
iteration variables. On each iteration,
the first variable is set to the array or slice index or
the first variable is set to the string, array or slice index or
map key, and the second variable, if present, is set to the corresponding
array element or map value.
string or array element or map value.
The types of the array or slice index (always <code>int</code>)
and element, or of the map key and value respectively,
must be assignment compatible to the iteration variables.
</p>
<p>
For strings, the "range" clause iterates over the Unicode code points
in the string. On successive iterations, the index variable will be the
position of successive UTF-8-encoded code points in the string, and
the second variable, of type <code>int</code>, will be the value of
the corresponding code point. If the iteration encounters an invalid
UTF-8 sequence, the second variable will be <code>0xFFFD</code>,
the Unicode replacement character, and the next iteration will advance
a single byte in the string.
</p>
<p>
For channels, the identifier list must contain one identifier.
The iteration recieves values sent on the channel until the channel is closed;
it does not process the zero value sent before the channel is closed.