Returns the characters in a string in reverse order, recognizing surrogate pairs.
||A string or expression that evaluates to a string.
returns the characters in string
in reverse order. $WREVERSE
is functionally identical to $REVERSE
, except that $WREVERSE
recognizes surrogate pairs. You can use the $WISWIDE
function to determine if a string contains a surrogate pair.
A surrogate pair is a pair of 16-bit InterSystems IRIS character elements that together encode a single Unicode character. Surrogate pairs are used to represent certain ideographs which are used in Chinese, Japanese kanji, and Korean hanja. (Most commonly-used Chinese, kanji, and hanja characters are represented by standard 16-bit Unicode encodings.) Surrogate pairs provide InterSystems IRIS support for the Japanese JIS X0213:2004 (JIS2004) encoding standard and the Chinese GB18030 encoding standard.
A surrogate pair consists of high-order 16-bit character element in the hexadecimal range D800 through DBFF, and a low-order 16-bit character element in the hexadecimal range DC00 through DFFF.
The $WREVERSE function counts a surrogate pair as a single character. The $REVERSE function treats a surrogate pair as two characters. In all other aspects, $WREVERSE and $REVERSE are functionally identical. However, because $REVERSE is generally faster than $WREVERSE, $REVERSE is preferable for all cases where a surrogate pair is not likely to be encountered.
For further details on reversing strings, refer to the $REVERSE
The following example shows how $WREVERSE treats a surrogate pair as a single character:
WRITE !,"String before reversing:"
WRITE !,"$WREVERSE did not reverse surrogate pair:"
WRITE !,"$REVERSE reversed surrogate pair:"
Content Date/Time: 2019-08-20 05:45:45