MAINT: Unify polynomial addition and subtraction functions

These functions are all the same - the algorithm used does not care about the basis.

7 files changed, 39 insertions, 114 deletions

diff --git a/numpy/polynomial/chebyshev.py b/numpy/polynomial/chebyshev.py
index 0eef90177..6fbdab065 100644
--- a/numpy/polynomial/chebyshev.py
+++ b/numpy/polynomial/chebyshev.py
@@ -583,15 +583,7 @@ def chebadd(c1, c2):
     array([4., 4., 4.])
 
     """
-    # c1, c2 are trimmed copies
-    [c1, c2] = pu.as_series([c1, c2])
-    if len(c1) > len(c2):
-        c1[:c2.size] += c2
-        ret = c1
-    else:
-        c2[:c1.size] += c1
-        ret = c2
-    return pu.trimseq(ret)
+    return pu._add(c1, c2)
 
 
 def chebsub(c1, c2):
@@ -635,16 +627,7 @@ def chebsub(c1, c2):
     array([ 2.,  0., -2.])
 
     """
-    # c1, c2 are trimmed copies
-    [c1, c2] = pu.as_series([c1, c2])
-    if len(c1) > len(c2):
-        c1[:c2.size] -= c2
-        ret = c1
-    else:
-        c2 = -c2
-        c2[:c1.size] += c1
-        ret = c2
-    return pu.trimseq(ret)
+    return pu._sub(c1, c2)
 
 
 def chebmulx(c):
diff --git a/numpy/polynomial/hermite.py b/numpy/polynomial/hermite.py
index 3767a80fc..5eabcfc66 100644
--- a/numpy/polynomial/hermite.py
+++ b/numpy/polynomial/hermite.py
@@ -326,15 +326,7 @@ def hermadd(c1, c2):
     array([2., 4., 6., 4.])
 
     """
-    # c1, c2 are trimmed copies
-    [c1, c2] = pu.as_series([c1, c2])
-    if len(c1) > len(c2):
-        c1[:c2.size] += c2
-        ret = c1
-    else:
-        c2[:c1.size] += c1
-        ret = c2
-    return pu.trimseq(ret)
+    return pu._add(c1, c2)
 
 
 def hermsub(c1, c2):
@@ -374,16 +366,7 @@ def hermsub(c1, c2):
     array([0.,  0.,  0.,  4.])
 
     """
-    # c1, c2 are trimmed copies
-    [c1, c2] = pu.as_series([c1, c2])
-    if len(c1) > len(c2):
-        c1[:c2.size] -= c2
-        ret = c1
-    else:
-        c2 = -c2
-        c2[:c1.size] += c1
-        ret = c2
-    return pu.trimseq(ret)
+    return pu._sub(c1, c2)
 
 
 def hermmulx(c):
diff --git a/numpy/polynomial/hermite_e.py b/numpy/polynomial/hermite_e.py
index 228396457..af12ad909 100644
--- a/numpy/polynomial/hermite_e.py
+++ b/numpy/polynomial/hermite_e.py
@@ -327,15 +327,7 @@ def hermeadd(c1, c2):
     array([2.,  4.,  6.,  4.])
 
     """
-    # c1, c2 are trimmed copies
-    [c1, c2] = pu.as_series([c1, c2])
-    if len(c1) > len(c2):
-        c1[:c2.size] += c2
-        ret = c1
-    else:
-        c2[:c1.size] += c1
-        ret = c2
-    return pu.trimseq(ret)
+    return pu._add(c1, c2)
 
 
 def hermesub(c1, c2):
@@ -375,16 +367,7 @@ def hermesub(c1, c2):
     array([0., 0., 0., 4.])
 
     """
-    # c1, c2 are trimmed copies
-    [c1, c2] = pu.as_series([c1, c2])
-    if len(c1) > len(c2):
-        c1[:c2.size] -= c2
-        ret = c1
-    else:
-        c2 = -c2
-        c2[:c1.size] += c1
-        ret = c2
-    return pu.trimseq(ret)
+    return pu._sub(c1, c2)
 
 
 def hermemulx(c):
diff --git a/numpy/polynomial/laguerre.py b/numpy/polynomial/laguerre.py
index dec469c17..378dd4c46 100644
--- a/numpy/polynomial/laguerre.py
+++ b/numpy/polynomial/laguerre.py
@@ -324,15 +324,7 @@ def lagadd(c1, c2):
 
 
     """
-    # c1, c2 are trimmed copies
-    [c1, c2] = pu.as_series([c1, c2])
-    if len(c1) > len(c2):
-        c1[:c2.size] += c2
-        ret = c1
-    else:
-        c2[:c1.size] += c1
-        ret = c2
-    return pu.trimseq(ret)
+    return pu._add(c1, c2)
 
 
 def lagsub(c1, c2):
@@ -372,16 +364,7 @@ def lagsub(c1, c2):
     array([0.,  0.,  0.,  4.])
 
     """
-    # c1, c2 are trimmed copies
-    [c1, c2] = pu.as_series([c1, c2])
-    if len(c1) > len(c2):
-        c1[:c2.size] -= c2
-        ret = c1
-    else:
-        c2 = -c2
-        c2[:c1.size] += c1
-        ret = c2
-    return pu.trimseq(ret)
+    return pu._sub(c1, c2)
 
 
 def lagmulx(c):
diff --git a/numpy/polynomial/legendre.py b/numpy/polynomial/legendre.py
index 5f8ce53a3..29b5892a1 100644
--- a/numpy/polynomial/legendre.py
+++ b/numpy/polynomial/legendre.py
@@ -356,15 +356,7 @@ def legadd(c1, c2):
     array([4.,  4.,  4.])
 
     """
-    # c1, c2 are trimmed copies
-    [c1, c2] = pu.as_series([c1, c2])
-    if len(c1) > len(c2):
-        c1[:c2.size] += c2
-        ret = c1
-    else:
-        c2[:c1.size] += c1
-        ret = c2
-    return pu.trimseq(ret)
+    return pu._add(c1, c2)
 
 
 def legsub(c1, c2):
@@ -408,16 +400,7 @@ def legsub(c1, c2):
     array([ 2.,  0., -2.])
 
     """
-    # c1, c2 are trimmed copies
-    [c1, c2] = pu.as_series([c1, c2])
-    if len(c1) > len(c2):
-        c1[:c2.size] -= c2
-        ret = c1
-    else:
-        c2 = -c2
-        c2[:c1.size] += c1
-        ret = c2
-    return pu.trimseq(ret)
+    return pu._sub(c1, c2)
 
 
 def legmulx(c):
diff --git a/numpy/polynomial/polynomial.py b/numpy/polynomial/polynomial.py
index f63d9dd74..8a2cffc15 100644
--- a/numpy/polynomial/polynomial.py
+++ b/numpy/polynomial/polynomial.py
@@ -224,15 +224,7 @@ def polyadd(c1, c2):
     28.0
 
     """
-    # c1, c2 are trimmed copies
-    [c1, c2] = pu.as_series([c1, c2])
-    if len(c1) > len(c2):
-        c1[:c2.size] += c2
-        ret = c1
-    else:
-        c2[:c1.size] += c1
-        ret = c2
-    return pu.trimseq(ret)
+    return pu._add(c1, c2)
 
 
 def polysub(c1, c2):
@@ -269,16 +261,7 @@ def polysub(c1, c2):
     array([ 2.,  0., -2.])
 
     """
-    # c1, c2 are trimmed copies
-    [c1, c2] = pu.as_series([c1, c2])
-    if len(c1) > len(c2):
-        c1[:c2.size] -= c2
-        ret = c1
-    else:
-        c2 = -c2
-        c2[:c1.size] += c1
-        ret = c2
-    return pu.trimseq(ret)
+    return pu._sub(c1, c2)
 
 
 def polymulx(c):
diff --git a/numpy/polynomial/polyutils.py b/numpy/polynomial/polyutils.py
index 1d5390984..d8e922b0a 100644
--- a/numpy/polynomial/polyutils.py
+++ b/numpy/polynomial/polyutils.py
@@ -573,3 +573,30 @@ def _div(mul_f, c1, c2):
             rem = rem[:-1] - q*p[:-1]
             quo[i] = q
         return quo, trimseq(rem)
+
+
+def _add(c1, c2):
+    """ Helper function used to implement the ``<type>add`` functions. """
+    # c1, c2 are trimmed copies
+    [c1, c2] = as_series([c1, c2])
+    if len(c1) > len(c2):
+        c1[:c2.size] += c2
+        ret = c1
+    else:
+        c2[:c1.size] += c1
+        ret = c2
+    return trimseq(ret)
+
+
+def _sub(c1, c2):
+    """ Helper function used to implement the ``<type>sub`` functions. """
+    # c1, c2 are trimmed copies
+    [c1, c2] = as_series([c1, c2])
+    if len(c1) > len(c2):
+        c1[:c2.size] -= c2
+        ret = c1
+    else:
+        c2 = -c2
+        c2[:c1.size] += c1
+        ret = c2
+    return trimseq(ret)