From ac3682813da3e9400fd19d5e13d2d6ca2e7d557b Mon Sep 17 00:00:00 2001
From: Antonio Jimenez Pastor <antonio@ebook.dk-compmath.jku.at>
Date: Tue, 19 Jun 2018 11:24:34 +0200
Subject: [PATCH] Added the method random_element to the class DDRing

---
 ajpastor/dd_functions/ddFunction.py | 57 +++++++++++++++++++++++++++----------
 1 file changed, 42 insertions(+), 15 deletions(-)

diff --git a/ajpastor/dd_functions/ddFunction.py b/ajpastor/dd_functions/ddFunction.py
index c02ac7c..d22988c 100644
--- a/ajpastor/dd_functions/ddFunction.py
+++ b/ajpastor/dd_functions/ddFunction.py
@@ -341,20 +341,6 @@ class DDRing (Ring_w_Sequence, IntegralDomain):
         if(isinstance(S, DDRing)):
             return S.depth() <= self.depth();
         
-        #coer = None;
-        #if(isinstance(S, DDRing)):
-        #    coer = self.base()._coerce_map_from_(S.base());
-        #elif(S == self.base()):
-        #    coer = True;
-        #elif(isinstance(S, sage.symbolic.ring.SymbolicRing)):
-        #    coer = True;
-        #else:
-        #    coer = self.base()._coerce_map_from_(S);
-        #    
-        #if(not(coer is False) and not(coer is None)):
-        #    return True;
-        #return None;
-        
     def __is_polynomial(self, S):
         from sage.rings.polynomial.polynomial_ring import is_PolynomialRing as isUniPolynomial;
         from sage.rings.polynomial.multi_polynomial_ring import is_MPolynomialRing as isMPolynomial;
@@ -545,7 +531,48 @@ class DDRing (Ring_w_Sequence, IntegralDomain):
             Method inherited from Ring SAGE class. It returns an example of object that is in the DDRing. It simply returns the 1 element.        
         '''
         return self.one();
-        
+    
+    def random_element(self,**kwds):
+        '''
+            Method to compute a random element in this ring. This method relies in a random generator of the self.base() ring and a generator of
+            elements of the ring self.base_ring().
+            This method accepts different named arguments:
+		- "min_order": minimal order for the equation we would get (default to 1)
+		- "max_order": maximal order for the equation we would get (default to 3)
+		- "simple": if True, the leading coefficient will always be one (default True)
+        '''
+	## Getting the arguments values
+	min_order = kwds.get("min_order", 1);
+	max_order = kwds.get("max_order", 3);
+	simple = kwds.get("simple", True);
+
+	## Checking the argument values
+	min_order = max(min_order,0); ## Need at least order 1
+	max_order = max(min_order, max_order); ## At least the maximal order must be equal to the minimal
+	if(simple != True and simple != False):
+            simple = False;
+
+        ## Computing the list of coefficients
+	R = self.base(); S = self.base_field;
+        coeffs = [R.random_element() for i in range(randint(min_order,max_order))];
+	
+	init_values = [0];
+	while(init_values[0] == 0):
+            init_values[0] = S.random_element();
+
+	## If we want simple elements, we can compute the initial values directly
+	if(simple):
+	    coeffs[-1] = R.one();
+	    init_values += [S.random_element() for i in range(len(coeffs)-2)];
+	    return self.element(coeffs,init_values);
+	## Otherwise, we need to know the initial value condition
+        equation = self.element(coeffs).equation;
+        warnings.warn("Not-simple random element not implemented. Returning zero", DDFunctionWarning, stacklevel=_sage_const_2);
+
+	return self.zero();
+
+	
+   
     def characteristic(self):
         '''
             Method inherited from the Ring SAGE class. It returns the characteristic of the coefficient ring.
-- 
2.1.4