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Error in rising_factorial
 
  
 
  
 
 
 
 
 
 
    
        
        asked 9 years ago  
 
 Peter Luschny gravatar image  
 
 
 
 
    
        
        updated 9 years ago  
 
 
 
 
 
print [rising_factorial(n,n) for n in (0..5)]
print [rising_factorial(n,n) for n in range(6)]
 
I think both forms should give the same result. But the output is: 
 
[1, 1, 6, 60, 840, 15120]
AttributeError: 'int' object has no attribute 'parent'
 
Edit: The same error is thrown for falling_factorial. Note that the factorial function does not
assume Sage-integers. This is a confusing inconsistency in the interface, at least.
 
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        answered 9 years ago  
 
 eric_g gravatar image  
 
 
 
 
 
This is because (i) range(6) returns a list of Python integers (int), contrary to (0..5), which is a generator of Sage integers (Integer), and (ii) the function rising_factorial is expecting Sage integers. To get the expected behavior, you should replace range(6) by srange(6) (which returns Sage integers). 
 
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But should this function take ints and coerce them?
kcrisman gravatar imagekcrisman (
    
        9 years ago
    )
Thanks Eric, I know the workaround as my first line shows. But this is a blatant bug because rising_factorial(0,0) = 1 no matter what technical type of integer is used.
Peter Luschny gravatar imagePeter Luschny (
    
        9 years ago
    )
@kcrisman: sure, I'll open a ticket for this tomorrow. 
@Peter: rising_factorial(0,0) works because Sage's preparser transforms the 0's into Sage integers, as you can see by means of the function preparse:
sage: preparse("rising_factorial(0,0)")
'rising_factorial(Integer(0),Integer(0))'
eric_g gravatar imageeric_g (
    
        9 years ago
    )
This is now http://trac.sagemath.org/ticket/20075
eric_g gravatar imageeric_g (
    
        9 years ago
    )
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        answered 8 years ago  
 
 eric_g gravatar image  
 
 
 
 
 
The ticket has been merged in SageMath 7.1. So if you download the latest version of SageMath, the problem has disappeared.
 
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        Asked:  9 years ago  
 
 
        Seen: 670 times 
 

        Last updated: Feb 16 '16 
 
 
 
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