Changeset 7820:3af2c144d35a

Timestamp:

12/20/07 12:15:58 (5 years ago)

Author:

William Stein <wstein@…>

Branch:

default

Tags:

2.9.1.alpha2

Message:

Trac #1569 -- fix solve bug that Brandon Barker reported

File:

• sage/calculus/equations.py (modified) (3 diffs)

sage/calculus/equations.py

@@ -727 +727 @@
 
 def solve(f, *args, **kwds):
-    """
+    r"""
     Algebraically solve an equation of system of equations for given variables.
 
@@ -734 +734 @@
         *args -- variables to solve for.
         solution_dict = True -- return a list of dictionaries containing the solutions.
+
     EXAMPLES:
         sage: x, y = var('x, y')
@@ -760 +761 @@
         0.000 , 1.00
 
+    If True appears in the list of equations it is ignored, and if
+    False appears in the list then no solutions are returned.  E.g.,
+    note that the first \code{3==3} evaluates to True, not to a symbolic
+    equation.  
+    
+        sage: solve([3==3, 1.00000000000000*x^3 == 0], x)
+        [x == 0]
+        sage: solve([1.00000000000000*x^3 == 0], x)
+        [x == 0]
+
+    Here, the first evaluates to False, so there are no solutions:
+        sage: solve([1==3, 1.00000000000000*x^3 == 0], x)
+        []
 
     """
     if isinstance(f, (list, tuple)):
+        f = [s for s in f if s is not True]
+        for s in f:
+            if s is False:
+                return []
+            
         m = maxima(list(f))
         try: