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Function std.utf.stride

Calculate the length of the UTF sequence starting at index in str.

uint stride(S) (
  auto ref S str,
  size_t index
)
if (is(S : const(char[])) || isRandomAccessRange!S && is(immutable(ElementType!S) == immutable(char)));

uint stride(S) (
  auto ref S str
)
if (is(S : const(char[])) || isInputRange!S && is(immutable(ElementType!S) == immutable(char)));

uint stride(S) (
  auto ref S str,
  size_t index
)
if (is(S : const(wchar[])) || isRandomAccessRange!S && is(immutable(ElementType!S) == immutable(wchar)));

uint stride(S) (
  auto ref S str
) pure @safe
if (is(S : const(wchar[])));

uint stride(S) (
  auto ref S str
)
if (isInputRange!S && is(immutable(ElementType!S) == immutable(wchar)) && !is(S : const(wchar[])));

uint stride(S) (
  auto ref S str,
  size_t index = 0
)
if (is(S : const(dchar[])) || isInputRange!S && is(immutable(ElementEncodingType!S) == immutable(dchar)));

Parameters

NameDescription
str input range of UTF code units. Must be random access if index is passed
index starting index of UTF sequence (default: 0)

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 the start of a valid UTF sequence.

Note

stride will only analyze the first str[index] 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 index + stride(str, index) <= str.length.

Example

writeln("a".stride); // 1
writeln("λ".stride); // 2
writeln("aλ".stride); // 1
writeln("aλ".stride(1)); // 2
writeln("𐐷".stride); // 4

Authors

Walter Bright and Jonathan M Davis

License

Boost License 1.0.