mat2.transpose

bpl · May 3, 2012 · 5198b9b · 5198b9b
1 parent 35b31aa
commit 5198b9b
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diff --git a/gl-matrix.js b/gl-matrix.js
@@ -2586,6 +2586,30 @@
         return dest;
     };
 
+    /**
+     * Transposes a mat2 (flips the values over the diagonal)
+     *
+     * @param {mat2} mat mat2 to transpose
+     * @param {mat2} [dest] mat2 receiving transposed values. If not specified result is written to mat
+     *
+     * @param {mat2} dest if specified, mat otherwise
+     */
+    mat2.transpose = function (mat, dest) {
+        // If we are transposing ourselves we can skip a few steps but have to cache some values
+        if (!dest || mat === dest) {
+            var a00 = mat[1];
+            mat[1] = mat[2];
+            mat[2] = a00;
+            return mat;
+        }
+
+        dest[0] = mat[0];
+        dest[1] = mat[2];
+        dest[2] = mat[1];
+        dest[3] = mat[3];
+        return dest;
+    };
+
     /*
      * Exports
      */

diff --git a/spec/javascripts/mat2_spec.js b/spec/javascripts/mat2_spec.js
@@ -43,4 +43,20 @@ describe("mat2", function() {
       it("should set result to identity", function() { expect(result).toBeEqualish([1, 0, 0, 1]); });
     });
   });
+
+  describe("transpose", function() {
+    describe("with dest", function() {
+      beforeEach(function() { result = mat2.transpose(a, dest); });
+      it("should set dest to transpose", function() { expect(dest).toBeEqualish([1, 3, 2, 4]); });
+      it("should return dest", function() { expect(result).toBe(dest); });
+      it("should not alter a", function() { expect(a).toBeEqualish([1, 2, 3, 4]); });
+    });
+
+    describe("without dest", function() {
+      beforeEach(function() { result = mat2.transpose(a); });
+      it("should set a to transpose", function() { expect(a).toBeEqualish([1, 3, 2, 4]); });
+      it("should return a", function() { expect(result).toBe(a); });
+    });
+  });
+
 });