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

Tim Peters tim.one at comcast.net
Mon Apr 19 10:57:52 EDT 2004

[Edward Loper]

... - I do believe that there will be use cases for exponents outside this range. Just because there's no physical quantities that are reasonably measured with these numbers, doesn't mean that there won't be abstract quantities that are reasonably measured with huge numbers.

You don't have a real use case, Edward (if you did, you would have given it by now ). YAGNI. Note that GNU GMP's arbitrary-precision float types also have bounds on exponent magnitude (but not on precision) -- this is conventional.

- I don't believe that signaling an error when a number goes outside this range will help catch any errors. What type of error are we expecting to catch here?

Overflow, and possibly underflow. Typical when a correct iterative algorithm is fed an input outside its radius of convergence, or an incorrect iterative algorithm is fed anything.

If this is such a problem, then why doesn't long also have a max/min?

For the same reason Decimal doesn't have a bound on precision: exact calculations can require any number of digits. Exponents kick in when the calculation becomes approximate (when precision is exceeded).

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