macOS Number formatting? Beginner question, decimals.

What language?

I assume we are using C (or Objective C) here.

This should work (I've not tested it though):

At the end wholePart should be 3, fractionalPart should be 0.14.

if it is C-like, try fmod w/ 1.0 as the 2nd operator for the decimal part, then floor for the whole number.

-Lee

If you want to get 3 and 14 returned and the number is a string you can use a string splitter such as NSString's componentsSeparatedByString: with the separator as a dot.

I would strongly suggest going with robbie duncan's way. Using a formatter to convert to a string then separating the string and converting back to a number is much more work (for you and your system) than just using math functions and scalar values. It could also be a problem if the program is used with different international settings (that use something other than . for the symbol) unless you spend the time configuring the formatter first.

Once you start forming habits, they can be hard to get away from when you get into larger apps. You are probably going to need the math.h functions sometime, so you might as well learn them soon.


The functions can be helpful when you need to round values to specific increments. To round for time increments for example:


All I usually use are floor(), ceil(), and round(). For the float version, just add "f" to the end. ie. floorf(), ceilf(), roundf().

Best of luck

lucasgladding said:

I would strongly suggest going with robbie duncan's way. Using a formatter to convert to a string then separating the string and converting back to a number is much more work (for you and your system) than just using math functions and scalar values.

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He wants the three and 14 not 3 and 0.14 I think, and that is much harder if you don't do it the string way. Anyway you shouldn't ever performance tweak until you know if it matters, but you should just do it in the easiest way.

lucasgladding said:

It could also be a problem if the program is used with different international settings (that use something other than . for the symbol) unless you spend the time configuring the formatter first.

Click to expand...

Good point, Europeans use , for example. You should get the number separator rather than assume its a . I believe you can do this with

This will need testing however...

Eraserhead said:

He wants the three and 14 not 3 and 0.14 I think, and that is much harder if you don't do it the string way.

Click to expand...

True enough. It does depend on whether Alfons is always working with the same precision. I can't think of many instances where .14 and .000014 should be considered the same number, but I am sure cases exist.

If the precision is known, you can always get the number with roundf(value * 10 * precision).

Eraserhead said:

Anyway you shouldn't ever performance tweak until you know if it matters, but you should just do it in the easiest way.

Click to expand...

Agreed about performance tweaking, but we are discussing unwritten code in this case. Performance implications should be considered in planning, though they don't need to be the primary objective. Besides, "the easiest way" could mean quite a few things. If an application is any more than an exercise, the developer has a responsibility to his/her users to understand the tools available for the job.

My apologies for the attitude in my last post, the best way does depend on the situation. That said, new Cocoa developers (including myself years ago) often think that everything needs to go through the NS, CG, CA, etc classes in order to be appropriate for the application.