[expansion] fix expand_sympy if x-expansion starts lower than `…

…`1/x``
gudrunhe · May 7, 2018 · e84343b · e84343b
1 parent 3a7ea5a
commit e84343b
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diff --git a/pySecDec/expansion.py b/pySecDec/expansion.py
@@ -344,7 +344,10 @@ def recursion(expression, variables, orders, index):
                 # all higher orders are exactly zero
                 truncated = False
                 break
-            current_term_order = sp.poly(next_term, variable).monoms()[0][0]
+            try:
+                current_term_order = sp.poly(next_term, variable).monoms()[0][0]
+            except sp.PolynomialError:
+                current_term_order = -sp.poly(next_term**-1, variable).monoms()[0][0]
             # if some intermediate orders are zero, append zeros to the expansion
             while current_order < current_term_order and current_order <= order:
                 coeffs.append(_sympy_zero)

diff --git a/pySecDec/test_expansion.py b/pySecDec/test_expansion.py
@@ -280,3 +280,27 @@ def test_missing_intermediate_order(self):
 
         for coeff in expansion.coeffs:
             self.assertTrue(isinstance(coeff, sp.Expr))
+
+    #@attr('active')
+    def test_higher_pole(self):
+        expression = 'gamma(eps)/eps'
+        variables = ['eps']
+
+        expansion = expand_sympy(expression, variables, orders=[0])
+
+        target_expansion_expolist = np.arange(3).reshape([3,1]) - 2
+        target_expansion_coeffs = [
+                                      '1',                         # eps ** -2
+                                      '-EulerGamma',               # eps ** -1
+                                      'EulerGamma**2/2 + pi**2/12' # eps **  0
+                                  ]
+        target_expansion = Polynomial(target_expansion_expolist, target_expansion_coeffs, ['eps'])
+
+        self.assertEqual( sp.sympify(expansion - target_expansion).simplify() , 0 )
+
+        np.testing.assert_array_equal(expansion.expolist, target_expansion.expolist)
+        np.testing.assert_array_equal(expansion.coeffs, target_expansion.coeffs)
+        self.assertTrue(expansion.truncated is True)
+
+        for coeff in expansion.coeffs:
+            self.assertTrue(isinstance(coeff, sp.Expr))