implement coefficient_of_n (for __getitem__)

Author: dkrenn

src/sage/combinat/k_regular_sequence.py

@@ -238,7 +238,7 @@ def _repr_(self):
             preview=10)
 
     @cached_method
-    def __getitem__(self, n, **kwds):
+    def coefficient_of_n(self, n, **kwds):
         r"""
         Return the `n`-th entry of this sequence.
 
@@ -256,6 +256,11 @@ def __getitem__(self, n, **kwds):
             sage: S[7]
             3
 
+        This is equivalent to::
+
+            sage: S.coefficient_of_n(7)
+            3
+
         TESTS::
 
             sage: S[-1]
@@ -279,6 +284,8 @@ def __getitem__(self, n, **kwds):
         """
         return self.coefficient_of_word(self.parent()._n_to_index_(n), **kwds)
 
+    __getitem__ = coefficient_of_n
+
     def __iter__(self):
         r"""
         Return an iterator over the coefficients of this sequence.
@@ -521,7 +528,7 @@ def subsequence(self, a, b):
 
         zero_M = self.mu[0].parent().zero()
         zero_R = self.right.parent().zero()
-        # Let v(n) = self.__getitem__(n, multiply_left=False)
+        # Let v(n) = self.coefficient_of_n(n, multiply_left=False)
         rule = {}
         # We will construct `kernel` and `rule` in such a way that for all
         # c in `kernel`,
@@ -557,7 +564,7 @@ def matrix_row(r, c):
                 b.get(c, 0) * self.left
                 for c in kernel)),
             vector(chain.from_iterable(
-                (self.__getitem__(c, multiply_left=False) if c >= 0 else zero_R)
+                (self.coefficient_of_n(c, multiply_left=False) if c >= 0 else zero_R)
                 for c in kernel)))
 
         return result
@@ -1265,8 +1272,7 @@ def guess(self, f, n_verify=100, max_exponent=10, sequence=None):
             seq = lambda m: vector([])
         else:
             mu = [M.rows() for M in sequence.mu]
-            seq = lambda m: (sequence._mu_of_word_(self._n_to_index_(m))
-                             * sequence.right)
+            seq = lambda m: sequence.coefficient_of_n(m, multiply_left=False)
             logger.info('including %s', sequence)
 
         zero = domain(0)