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Function std.utf.strideBack
Calculate the length of the UTF sequence ending one code unit before
index
in str
.
uint strideBack(S)
(
auto ref S str,
size_t index
)
if (is(S : const(char[])) || isRandomAccessRange!S && is(immutable(ElementType!S) == immutable(char)));
uint strideBack(S)
(
auto ref S str
)
if (is(S : const(char[])) || isRandomAccessRange!S && hasLength!S && is(immutable(ElementType!S) == immutable(char)));
uint strideBack(S)
(
auto ref S str
)
if (isBidirectionalRange!S && is(immutable(ElementType!S) == immutable(char)) && !isRandomAccessRange!S);
uint strideBack(S)
(
auto ref S str,
size_t index
)
if (is(S : const(wchar[])) || isRandomAccessRange!S && is(immutable(ElementType!S) == immutable(wchar)));
uint strideBack(S)
(
auto ref S str
)
if (is(S : const(wchar[])) || isBidirectionalRange!S && is(immutable(ElementType!S) == immutable(wchar)));
uint strideBack(S)
(
auto ref S str,
size_t index
)
if (isRandomAccessRange!S && is(immutable(ElementEncodingType!S) == immutable(dchar)));
uint strideBack(S)
(
auto ref S str
)
if (isBidirectionalRange!S && is(immutable(ElementEncodingType!S) == immutable(dchar)));
Parameters
Name | Description |
---|---|
str | bidirectional range of UTF code units. Must be random access if
index is passed |
index | index one past end of UTF sequence (default: str ) |
Returns
The number of code units in the UTF sequence. For UTF-8, this is a value between 1 and 4 (as per RFC 3629, section 3). For UTF-16, it is either 1 or 2. For UTF-32, it is always 1.
Throws
May throw a UTFException
if str[index]
is not one past the
end of a valid UTF sequence.
Note
strideBack
will only analyze the element at str[index - 1]
element. It will not fully verify the validity of the UTF sequence, nor
even verify the presence of the sequence: it will not actually
guarantee that strideBack(str, index) <= index
.
Example
writeln("a" .strideBack); // 1
writeln("λ" .strideBack); // 2
writeln("aλ" .strideBack); // 2
writeln("aλ" .strideBack(1)); // 1
writeln("𐐷" .strideBack); // 4
Authors
License
Copyright © 1999-2022 by the D Language Foundation | Page generated by ddox.