Fix some busted comments and argument names.

diff --git a/string-lerp.js b/string-lerp.js
index 1aa89b0..fdf7df8 100644 (file)
--- a/string-lerp.js
+++ b/string-lerp.js
@@ -85,15 +85,15 @@
     }
 
     function diff(source, target, ins, del, sub) {
-        /** Create a diff between string source and target
+        /** Create a list of edits to turn source into target
 
-            ins, del, and sub are as passed to levenshtein
-         */
+            ins, del, and sub are as passed to costMatrix.
+        */
         return editPath(costMatrix(source, target, ins, del, sub), target);
     }
 
     function patch(diff, source) {
-        /** Apply the list of edits to s */
+        /** Apply a list of edits to source */
         var edit;
         var i;
 
@@ -117,15 +117,15 @@
 
     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 diffLerp(a, b, p) {
-        /** Interpolate between two strings based on edit operations
+    function diffLerp(source, target, amount ) {
+        /** Interpolate between two strings using edit operations
 
             This interpolation algorithm applys a partial edit of one
             string into the other. This produces nice looking results,
             but can take a significant amount of time and memory to
             compute the edits. It is not recommended for strings
             longer than a few hundred characters.
-         */
+        */
 
         // If given strings with astral codepoints or combining
         // characters, split them into arrays of "glyphs" first,
@@ -134,42 +134,38 @@
         // This split is not perfect for all languages, but at least
         // it won't create invalid surrogate pairs or orphaned
         // combining characters.
-        if (a.match && a.match(MULTI) || b.match && b.match(MULTI)) {
-            var ca = a.match(GLYPH) || [];
-            var cb = b.match(GLYPH) || [];
-            return diffLerp(ca, cb, p).join("");
+        if (source.match && (source.match(MULTI) || target.match(MULTI))) {
+            var sourceGlyphs = source.match(GLYPH) || [];
+            var targetGlyphs = target.match(GLYPH) || [];
+            return diffLerp(sourceGlyphs, targetGlyphs, amount).join("");
         }
 
         // 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 edits = diff(b, a, 2, 2, 3);
-        var partial = edits.slice(0, Math.round((1 - p) * edits.length));
-        return patch(partial, b);
+        var edits = diff(target, source, 2, 2, 3);
+        var partial = edits.slice(0, Math.round((1 - amount) * edits.length));
+        return patch(partial, target);
     }
 
     var NUMBERS = /(-?\d+(?:\.\d+)?)/g;
 
-    function areNumericTwins(a, b) {
-        /** Check if a and b differ only in numerals
-
-            A leading "-" counts as part of numbers; a leading "+"
-            does not. Numbers may contain a single ".", but no other
-            floating point syntax.
-        */
-        return a.replace(NUMBERS, "0") === b.replace(NUMBERS, "0");
+    function areNumericTwins(source, target) {
+        /** Check if a and b differ only in numerals */
+        return source.replace(NUMBERS, "0") === target.replace(NUMBERS, "0");
     }
 
-    function nlerp(a, b, p) {
-        return a + (b - a) * p;
+    function nlerp(source, target, amount) {
+        return source + (target - source) * amount;
     }
 
-    function numericLerp(a, b, p) {
-        /** Interpolate numerically between two strings containing numbers
+    function numericLerp(source, target, amount) {
+        /** Interpolate numerically between strings containing numbers
 
             Numbers may have a leading "-" and a single "." to mark
             the decimal point, but something must be after the ".".
+            No other floating point syntax (e.g. 1e6) is supported.
             If both of the numbers in a pair are integers, the result
             is clamped to an integer.
 
@@ -181,16 +177,23 @@
 
             Calling this functions on strings that differ in more than
             numerals gives undefined results.
-         */
-        var aParts = a.split(NUMBERS);
-        var bParts = b.split(NUMBERS);
-        for (var i = 1; i < aParts.length; i += 2) {
-            var part = nlerp(+aParts[i], +bParts[i], p);
-            if (aParts[i].indexOf(".") === -1 && bParts[i].indexOf(".") === -1)
+        */
+
+        // TODO: Try to preserve precision of the original numbers.
+        var sourceParts = source.split(NUMBERS);
+        var targetParts = target.split(NUMBERS);
+        var destParts = targetParts;
+        for (var i = 1; i < sourceParts.length; i += 2) {
+            var sourcePart = sourceParts[i];
+            var targetPart = targetParts[i];
+            var part = nlerp(+sourcePart, +targetPart, amount);
+            var sourcePoint = sourcePart.indexOf(".");
+            var targetPoint = targetPart.indexOf(".");
+            if (sourcePoint === -1 && targetPoint === -1)
                 part = Math.round(part);
-            aParts[i] = part.toString();
+            targetParts[i] = part.toString();
         }
-        return aParts.join("");
+        return targetParts.join("");
     }
 
     function fastLerp(a, b, p) {
@@ -203,7 +206,8 @@
 
         // TODO: Consider fast-pathing this even more for very large
         // strings, e.g. in the megabyte range. These are large enough
-        // that 
+        // that it should be fine to just pick a codepoint and search
+        // for the nearest glyph start.
         if (a.match(MULTI) || b.match(MULTI)) {
             var ca = a.match(GLYPH) || [];
             var cb = b.match(GLYPH) || [];