[Python-Dev] return type of __complex__

[Tres Seaver]

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On 10/19/2012 07:35 PM, Greg Ewing wrote:
> Antonio Cuni wrote:
>> Traceback (most recent call last): File "<stdin>", line 1, in
>> <module> TypeError: __complex__ should return a complex object
>> 
>> i.e., the complex constructor does not check that __complex__
>> returns an actual complex, while the cmath functions do.
> 
> Looks to me like cmath is being excessively finicky here. Why
> shouldn't a float be usable in *any* context expecting a complex?

Exactly:  float is perfectly Liskov-substituable for complex;  only
applications which do explicit type sniffing can tell the difference,
which makes the sniffing bogus.


Tres.
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Tres Seaver          +1 540-429-0999          tseaver at palladion.com
Palladion Software   "Excellence by Design"    http://palladion.com
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