I guess this is due to the fact the "subs" replaces the variables in the
result (after the expression is computed) not in the expression itself
whereas by directly entering the numbers it takes them as bools ( 0 being
False and others being True). So, I guess it is consistent.
On Saturday, April 5, 2014 9:32:36 AM UTC+5:30, Mehul Tikekar wrote:
>
> There seems to be some sort of inconsistency when using symbols vs
> literals -
>
> >>> ITE(True, 3, 4)
> True
> >>> a, b, c = symbols('a b c')
> >>> ITE(a, b, c).subs([(a, True), (b, 3), (c, 4)])
> 3
>
> On Friday, April 4, 2014 11:33:56 PM UTC-4, SAHIL SHEKHAWAT wrote:
>>
>> It is not necessary for all the arguments of ITE to be bool. If x,y and z
>> are all arbitrary variables (but not numbers) this is what it gives.
>> * >>> ITE(x,y,z)*
>> * Or(And(Not(x), z), And(x, y))*
>> And you are getting this error because of the above logical statement *(*you
>> can not add two logical statements but if by "+" you mean "Or" please use "
>> | "*)* But if instead of that like, i said earlier, if "Cond" in your
>> example is either* True *or *False* your statement will return* ( x + y
>> )*
>> * >>> ITE(True,x,y) + ITE(True,y,x)*
>> * x + y*
>>
>> And about x and y being a number, ITE does not support that . It takes
>> them as being bool.
>> The reason the arbitary variables work but number don't is that ITE is a
>> logical boolean function which converts number into bools whereas you can
>> use variables because they can be specified to be bools like
>> * >>>x = symbols(x,is_Boolean=True)*
>>
>> *I am not sure if we want numbers to be included in ITE or they are just
>> fine. it will be nice if other developers also comment.*
>> *Thanks*
>>
>> On Friday, April 4, 2014 9:55:58 PM UTC+5:30, Mehul Tikekar wrote:
>>>
>>> I am referring to the ITE function defined in sympy here:
>>> http://docs.sympy.org/dev/_modules/sympy/logic/boolalg.html#ITE. But it
>>> requires all three arguments to be boolean. When I try:
>>>
>>> cond, x, y = symbols('cond x y')
>>> ITE(cond, x, y) + ITE(cond, y, x)
>>>
>>> I get a TypeError: unsupported operand type(s) for +: 'Or' and 'Or'
>>>
>>> On Friday, April 4, 2014 12:17:00 PM UTC-4, SAHIL SHEKHAWAT wrote:
>>>>
>>>> I don't understand what you mean by boolean ITE function can you please
>>>> explain that?
>>>> BUT I think ITE work well if "cond" is a bool when "x" and "y" are
>>>> arbitary symbols. for example:
>>>> IN [1]:* ITE**(True, x , y)*
>>>> OUT [1]:* x*
>>>>
>>>> in the second part of your question if "cond" is a bool then yes ,*
>>>> ITE'(cond, a, b) + ITE'(cond, b, a) *will return* (a+b)*
>>>>
>>>>
>>>> On Fri, Apr 4, 2014 at 9:23 PM, Mehul Tikekar <[email protected]>wrote:
>>>>
>>>>> Hi,
>>>>> I am looking for a variant of the boolean ITE(cond, x, y) function.
>>>>> I need only "cond" to be a bool while "x" and "y" are arbitrary symbols
>>>>> (they could be numbers, for example). Does sympy have a function like
>>>>> that?
>>>>> If not, any ideas on how I can go about writing one? Ideally, it should
>>>>> also be able to do simplifications. For example, ITE'(cond, a, b) +
>>>>> ITE'(cond, b, a) should be simplified to (a + b).
>>>>>
>>>>> Mehul
>>>>>
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>>>>>
>>>>
>>>>
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