pow in fact didn't work for *any* interval with a negative part

computo-fc · computo-fc · commit a7f619e2e0de · 2014-03-19T17:55:59.000-06:00
diff --git a/src/python/interval.py b/src/python/interval.py
@@ -372,15 +372,16 @@ def __pow__(self, exponent):
         """
         inf = calc_inf()
 
-        if not 0 > self:        # not wholly negative
+        if self > 0:        # not wholly negative
 
             exponent = self.make_interval(exponent)
             return( exp(exponent * log(self)) )   # seems to work! EXCEPT for pure negative intervals
 
 
-        else:
+        elif 0 > self:
             if not exponent == int(exponent):  # noninteger exponent not allowed
                 print ("Negative intervals cannot be raised to a fractional power")
+                return  # Should throw error
 
 
         #
@@ -433,7 +434,7 @@ def __pow__(self, exponent):
                     return Interval( lower, upper )
 
                 elif 0 > self:
-                    print ("Negative intervals can not be raised to a fractional power")
+                    print ("Negative intervals cannot be raised to a fractional power")
 
                 else:
                     ctx.round = RoundDown
diff --git a/src/python/interval_tools.py b/src/python/interval_tools.py
@@ -49,12 +49,12 @@ def plot_interval_f( fun, x, pow2=0, num_points=101 ):
     The original function is plotted at num_points points
     """
     num_intervals = [ 2**p for p in range(pow2+1) ]
-    fact_alfa = 0.3 # num*1.0/num_intervals[-1]   # for plotting
 
     # plt.figure()
     # plt.subplot(1, 1, 1)
 
     for num in num_intervals:
+        fact_alfa = num * 1.0/num_intervals[-1]   # for plotting
 
         subdivided_intervals = split_interval( x, num )
         total_range = range_interval_f( fun, subdivided_intervals )
