Re: Number Formatting
Re: Number Formatting
- Subject: Re: Number Formatting
- From: Jon Hull <email@hidden>
- Date: Sun, 20 Jun 2004 16:23:46 -0700
I'm playing around with formatting numbers using +stringWithFormat:
and various format specifiers...
What I want is to be able to set a number to always be shown in
scientific notation, i.e.:
NSString *someString = [NSString stringWithFormat:@"%e", someNumber];
However, this places a strict precision on the number format, such
that if someNumber = 8000, someString will be @"8.0000000e+03". If I
use the %g specifier, it will create strings with a variable
precision, i.e. 8000000 = @"8e+06", but of course this is not always
in scientific notation. Aside from the argument for strict
significant digits, having all these extra zeros on %e and %f strings
is just plain ugly. How does %g provide such nicely formatted
numbers?
I obviously need to use some sort of NSNumberFormatter to get the
variable precision I desire, but I'm not seeing any methods in
NSNumberFormatter, NSNumber, NSDecimalNumber, etc. that will be at all
helpful. It seems like the only way to do what I want is to test the
string for unnecessary zeros in the NSFormatter, and then remove them.
How retarded... (Furthermore, I later plan to build in support for
engineering notation and significant digits, which will no doubt spawn
a host of new headaches.)
Unless someone here comes up with a better suggestion, I think it will
be time for me to make another framework that everyone can use for
this pretty basic functionality. Better suggestions?
It sounds to me like you want to subclass NSNumber or NSDecimalNumber
(maybe call it ScientificNumber) and add methods for sig-figs and any
other features you need. Then your NSFormatter subclass can use that
info to give you perfectly formatted strings (and create your
Scientific Numbers from strings). I know it sounds like more work...
but splitting it into two classes will make things cleaner (not to
mention much easier to update later).
If you have time, it sounds like this would make a useful IB Palette!
Thanks,
Jon
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