Uppercase variables are now put at the end of a polynome, and the start of a monomial.

src/rules/integrals.py

@@ -21,7 +21,7 @@ def choose_constant(integral):
         i += 2 if i == 98 else 1
         c = chr(i)
 
-    return L(c)
+    return L(c.upper())
 
 
 def solve_integral(integral, F):

src/rules/sort.py

@@ -26,6 +26,10 @@ def get_power_prop(node):
             return root.value, exp
 
 
+def is_upper(character):
+    return 'A' <= character <= 'Z'
+
+
 def swap_mono((left, right)):
     """
     Check if a pair of left and right multiplication factors in a monomial
@@ -46,6 +50,9 @@ def swap_mono((left, right)):
             # Same variable, compare exponents
             return left_exp > right_exp
 
+        if is_upper(left_var) != is_upper(right_var):
+            return is_upper(left_var) < is_upper(right_var)
+
         # Compare variable names alphabetically
         return left_var > right_var
 
@@ -99,6 +106,9 @@ def swap_poly((left, right)):
         # Same variable, compare exponents
         return left_exp < right_exp
 
+    if is_upper(left_var) != is_upper(right_var):
+        return is_upper(left_var) > is_upper(right_var)
+
     # Compare variable names alphabetically
     return left_var > right_var