add get_fornberg_coeffs

bfps/tools.py

@@ -71,36 +71,39 @@ def padd_with_zeros(
 
 try:
     import sympy as sp
+    rational0 = sp.Rational(0)
+    rational1 = sp.Rational(1)
+except ImportError:
+    rational0 = 0.0
+    rational1 = 1.0
 
-    def get_fornberg_coeffs(
-            x = None,
-            a = None):
-        N = len(a) - 1
-        d = []
-        for m in range(N+1):
-            d.append([])
-            for n in range(N+1):
-                d[m].append([])
-                for j in range(N+1):
-                    d[m][n].append(sp.Rational(0))
-        d[0][0][0] = sp.Rational(1)
-        c1 = sp.Rational(1)
-        for n in range(1, N+1):
-            c2 = sp.Rational(1)
-            for j in range(n):
-                c3 = a[n] - a[j]
-                c2 = c2*c3
-                for m in range(n+1):
-                    d[m][n][j] = ((a[n] - x)*d[m][n-1][j] - m*d[m-1][n-1][j]) / c3
+def get_fornberg_coeffs(
+        x = None,
+        a = None):
+    N = len(a) - 1
+    d = []
+    for m in range(N+1):
+        d.append([])
+        for n in range(N+1):
+            d[m].append([])
+            for j in range(N+1):
+                d[m][n].append(rational0)
+    d[0][0][0] = rational1
+    c1 = rational1
+    for n in range(1, N+1):
+        c2 = rational1
+        for j in range(n):
+            c3 = a[n] - a[j]
+            c2 = c2*c3
             for m in range(n+1):
-                d[m][n][n] = (c1 / c2)*(m*d[m-1][n-1][n-1] - (a[n-1] - x)*d[m][n-1][n-1])
-            c1 = c2
-        coeffs = []
-        for m in range(len(d)):
-            coeffs.append([])
-            for j in range(len(d)):
-                coeffs[-1].append(d[m][N][j])
-        return np.array(coeffs).astype(np.float)
-except ImportError:
-    print('didn\'t find sympy.')
+                d[m][n][j] = ((a[n] - x)*d[m][n-1][j] - m*d[m-1][n-1][j]) / c3
+        for m in range(n+1):
+            d[m][n][n] = (c1 / c2)*(m*d[m-1][n-1][n-1] - (a[n-1] - x)*d[m][n-1][n-1])
+        c1 = c2
+    coeffs = []
+    for m in range(len(d)):
+        coeffs.append([])
+        for j in range(len(d)):
+            coeffs[-1].append(d[m][N][j])
+    return np.array(coeffs).astype(np.float)