Menu
Search

API Documentation

version 2.108.0

overview

View source code
Display the source code in std/utf.d from which this page was generated on github.
Report a bug
If you spot a problem with this page, click here to create a Bugzilla issue.
Improve this page
Quickly fork, edit online, and submit a pull request for this page. Requires a signed-in GitHub account. This works well for small changes. If you'd like to make larger changes you may want to consider using local clone.

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

NameDescription
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.length)

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

Walter Bright and Jonathan M Davis

License

Boost License 1.0.