Hi Dave
Did you really leave two very-similar messages 3 minutes apart? Or are you using a broken gateway, like Google-groups, and it hiccoughed?
Sorry, I didn't intend to - flunky LH mouse microswitch!
Without knowing the type of the arguments being passed to the crosspoint() function, we cannot say. I can GUESS that they are int, long, or float. But you can find that out by examining the source that's calling it. Judging from the comments, I might guess they're int or long, and if so, only the division being done in the function produces floats. If that's the case, then you're limited to float's precision. if they are some other type (eg. Decimal), then indeed there might be special functions being called.
Well, the two scripts are only about an email page long each, shall I post them?
That import gets you access to the particular symbols it imports. Normal arithmetic on floats is already built in, and doesn't need an import.
Right! Thanks.
I'm assuming you're using CPython, and you say it's on XP. So presumably you're running an Intel (or Intel-compatible) processor with binary floating point built-in. That processor is the limit of float values in normal use. It's good to about 18 digits.
Sure, 32 bit uproc, intrinsic binary limit.
Exactly. It's a side-effect of the first import of the module. On subsequent imports, the pyc file is used, unless the py file has been modified meanwhile.
Ah! Thanks!
18 digits is what you should get if the code is as I describe. But if there are lots of fp operations you're not showing, then an error can gradually get larger. And with any finite precision, you have the risk from things such as subtracting two nearly-equal values, which will reduce the final precision.
AFAIK, it's all FP. inputs are integers, outputs range from -2.000000000000 to 2.000000000000
If you need more than 18, then go to the Decimal module, which lets you set the precision to arbitrary levels. You will see a substantial slowdown, of course, if you set the precision very high. if that becomes a problem, consider CPython 3.3, which has optimized that module. But try not to change too many things at once, as there are lots of changes between 2.7 and 3.3.
I think I'll need to from what you have said / pointed out - ie, for in excess of 'machine' precision, one needs to change base 10 floats to a higher base, do foo, then come back. Sounds daunting! John. _______________________________________________ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
