[Python-Dev] Decimal data type issues (original) (raw)

Batista, Facundo FBatista at uniFON.com.ar
Tue Apr 13 16:04:02 EDT 2004

[Michael Chermside]

#- > The issue is that this limit is artificial: #- [...] #- > So, should we impose an artificial limit to the exponent? #- > #- > This is important, as there're several cases where this #- > maximums are checked #- > and exceptions raised and/or the numbers get changed. #- #- I strongly prefer for my programming language not to impose #- aribtrary limits, however, I can't see myself using decimal #- to represent numbers with 1 billion digits. So IMHO, I would #- avoid the limit if possible, but if imposing the limit #- permitted substantial code simplification or performance #- improvements then I wouldn't complain. Much.

Actually, imposing the limit means more code and complexity, and I don't find any benefit. But as I answered to Paul, I'm searching for community agreement before changing functionality that I found in the implementation

#- I disagree. If x == y, then that should imply that hash(x) #- == hash(y). #- So hash(Decimal(25)) == hash(25) had better be true. On the other #- hand, hash(Decimal('-33')) CANNOT equal hash(Decimal('-33')), since #- the latter must equal hash(-33). And I'm not particularly concerned #- about floats... if it's easy to make the hashes equal for those few #- numbers which can be expressed EXACTLY as both a (binary) float and #- a (decimal) Decimal, then that's be "kinda nice", but since there #- are so few values which can be expressed exactly as both a float #- and a Decimal, I don't see it as a big issue.

So, while Decimal(25) == 25 is True, hash(Decimal(25)) should be equal to hash(25).

The detail is that you can NOT compare Decimal to floats or strings, so maybe we should not worry about them to give the same hashes.

I'm OK to make hash(int or long) == hash(Decimal(int or long)). But only to int or long, not float nor string.

Do you agree?

. Facundo

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