Ticket #7334: trac-7344-logcontract-2.patch

sage/symbolic/expression.pyx

@@ -5215 +5215 @@
         among the components of the expression for simplifications based on
         factoring and partial fraction expansions of exponents."
         
-        ALIAS: radical_simplify, simplify_radical, simplify_log,
-        log_simplify, exp_simplify, simplify_exp are all the same
+        ALIAS: radical_simplify, simplify_radical, 
+        exp_simplify, simplify_exp are all the same
         
         EXAMPLES::
         
@@ -5247 +5247 @@
         maxima.eval('domain: complex$')
         return res
 
-    radical_simplify = simplify_log = log_simplify = simplify_radical
+    radical_simplify = simplify_radical
     simplify_exp = exp_simplify = simplify_radical
 
+    def simplify_log(self,coeff='integers'):
+        r"""
+        Simplifies this symbolic expression, which can contain logs
+
+        INPUT::
+            self -- expression to be simplified
+
+            coeff -- if 'integers' then only integers multiples are 
+                     contracted as powers inside logarithm. If 'ratios', 
+                     then also quotients of integers are treated this way.        
+
+        
+        DETAILS: This uses the Maxima logcontract() command. From the
+        Maxima documentation: "Recursively scans the expression expr,
+        transforming subexpressions of the form a1*log(b1) +
+        a2*log(b2) + c into log(ratsimp(b1^a1 * b2^a2)) + c. The user
+        can control which coefficients are contracted by setting the
+        option logconcoeffp to the name of a predicate function of one
+        argument. E.g. if you like to generate SQRTs, you can do
+        logconcoeffp:'logconfun$ logconfun(m):=featurep(m,integer) or
+        ratnump(m)$ . Then logcontract(1/2*log(x)); will give
+        log(sqrt(x))."
+        
+        ALIAS: log_simplify is the same
+
+        EXAMPLES::
+        
+            sage: x,y,t=var('x y t')
+        
+        ::
+        
+            sage: f = log(x)+2*log(y)+1/2*log(t)
+            sage: f.simplify_log()
+            log(x*y^2) + 1/2*log(t)
+            sage: f.simplify_log(coeff='ratios')
+            log(sqrt(t)*x*y^2)
+        
+        """
+        from sage.calculus.calculus import maxima
+        maxima.eval('domain: real$')
+        if coeff == 'ratios':
+            maxima.eval('logconcoeffp:\'logconfun$')
+            maxima.eval('logconfun(m):=featurep(m,integer) or ratnump(m)$')
+        res = self.parent()(self._maxima_().logcontract())
+        maxima.eval('domain: complex$')
+        if coeff == 'ratios':
+            maxima.eval('logconcoeffp:false$')  
+        return res
+
+    log_simplify = simplify_log
+
 
     def factor(self, dontfactor=[]):
         """