Let simplify handle a/(b/c) (#1734)

Co-authored-by: Jos de Jong <[email protected]>
josdejong · Feb 4, 2020 · 88733f7 · 88733f7
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diff --git a/src/function/algebra/simplify.js b/src/function/algebra/simplify.js
@@ -317,7 +317,9 @@ export const createSimplify = /* #__PURE__ */ factory(name, dependencies, (
     // { l: '(n1/n2)/n3', r: 'n1/(n2*n3)' },
     // { l: '(n*n1)/(n*n2)', r: 'n1/n2' },
 
-    { l: '1*n', r: 'n' } // this pattern can be produced by simplifyConstant
+    { l: '1*n', r: 'n' }, // this pattern can be produced by simplifyConstant
+
+    { l: 'n1/(n2/n3)', r: '(n1*n3)/n2' }
 
   ]
 

diff --git a/test/unit-tests/function/algebra/simplify.test.js b/test/unit-tests/function/algebra/simplify.test.js
@@ -255,6 +255,13 @@ describe('simplify', function () {
     simplifyAndCompare('myMultiArg(x, y, z, w)', 'myMultiArg(x, y, z, w)')
   })
 
+  it('should simplify a/(b/c)', function () {
+    simplifyAndCompare('x/(x/y)', 'y')
+    simplifyAndCompare('x/(y/z)', 'x * z/y')
+    simplifyAndCompare('(x + 1)/((x + 1)/(z + 3))', 'z + 3')
+    simplifyAndCompare('(x + 1)/((y + 2)/(z + 3))', '(x + 1) * (z + 3)/(y + 2)')
+  })
+
   it('should support custom rules', function () {
     const node = math.simplify('y+x', [{ l: 'n1-n2', r: '-n2+n1' }], { x: 5 })
     assert.strictEqual(node.toString(), 'y + 5')