+ var MULTI = /[\uD800-\uDBFF][\uDC00-\uDFFF]|[\u0300-\u036F\u1DC0-\u1DFF\u20D0-\u20FF\uFE20-\uFE2F]/;
+
+ var GLYPH = /([\0-\u02FF\u0370-\u1DBF\u1E00-\u20CF\u2100-\uD7FF\uDC00-\uFE1F\uFE30-\uFFFF]|[\uD800-\uDBFF][\uDC00-\uDFFF]|[\uD800-\uDBFF])([\u0300-\u036F\u1DC0-\u1DFF\u20D0-\u20FF\uFE20-\uFE2F]*)/g;
+
+ function diffLerpAstral(source, target, amount) {
+ // If given strings with astral codepoints or combining
+ // characters, split them into arrays of "glyphs" first,
+ // do the edit on the list of "glyphs", and rejoin them.
+ //
+ // This split is not perfect for all languages, but at least
+ // it won't create invalid surrogate pairs or orphaned
+ // combining characters.
+ var sourceGlyphs = source.match(GLYPH) || [];
+ var targetGlyphs = target.match(GLYPH) || [];
+ var edits = diff(targetGlyphs, sourceGlyphs, 2, 2, 3);
+ // The edit path works from the string end, forwards, because
+ // that's how Levenshtein edits work. To match LTR reading
+ // direction (and the behavior of fastLerp), swap the strings
+ // and invert the parameter when editing.
+ var partial = edits.slice(0, Math.round((1 - amount) * edits.length));
+ return patchArray(partial, targetGlyphs).join("");
+ }
+
+ function diffLerpBasic(source, target, amount) {
+ var edits = diff(target, source, 2, 2, 3);
+ // The edit path works from the string end, forwards, because
+ // that's how Levenshtein edits work. To match LTR reading
+ // direction (and the behavior of fastLerp), swap the strings
+ // and invert the parameter when editing.
+ var partial = edits.slice(0, Math.round((1 - amount) * edits.length));
+ return patchString(partial, target);
+ }
+
+ function diffLerp(source, target, amount) {
+ /** Interpolate between two strings using edit operations