On Wednesday, September 12, 2012 11:36:05 AM UTC-4, William wrote: > > On Wed, Sep 12, 2012 at 8:11 AM, Jori Mantysalo > <[email protected]<javascript:>> > wrote: > > On Wed, 12 Sep 2012, Dan Drake wrote: > > > >>> sage: 0.2 + 0.1 == 0.3 > >>> False > > > > > >> using an approximation -- and after the addition, the error is big > >> enough to return False. > ... > > > Incidentally, the Python Decimal module was designed to address this > issue: > > http://docs.python.org/library/decimal.html > > For example, > > sage: from decimal import Decimal as RealNumber > sage: 0.2 + 0.1 == 0.3 > True > > Arithmetic will be slower and many special functions won't work at > all. But if you're just doing basic arithmetic with decimal numbers, > it will have exactly the semantics you expect. > > sage: sin(0.2) > ... > TypeError: cannot coerce arguments: no canonical coercion from <class > 'decimal.Decimal'> to Symbolic Ring > > That this sort of thing doesn't work could actually be fixed if > somebody wanted to... > > It's now http://trac.sagemath.org/sage_trac/ticket/13453 for that mythological person who wants to.
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