div() for Floatingpoint number

[Sisyphuss]

Hello everyone,

I want a function F(), so that

F(0.154, 0.1)   = 0.1

F(0.154, 0.01) = 0.15

F(0.154, 0.003) = 0.153

I tried `div(a,b)*b`. However, I got:

div(0.128,0.0001) * 0.0001 = 0.1279

not equal to 0.1280

Any solution?

[Isaiah Norton]

See http://julia.readthedocs.org/en/latest/manual/integers-and-floating-point-numbers/#rounding-modes

and the rest of the discussion on that page.

[Stefan Karpinski]

What is the behavior of this function supposed to be? F(a,b) is the nearest multiple of b to a? I'm curious what definition is consistent with all three given examples.

[Sisyphuss]

Yes, precisely downwards nearest multiple.

The original idea is whether a function can return a value to a given precision (something like floor, round).

Furthermore, it will be more useful if it works for more general precision, say 0.05, 0.02, 0.03...

[Dan]

F(a,b) = floor(Int,a/b)*b

seems to fit the examples.

[Stefan Karpinski]

On Fri, Oct 9, 2015 at 9:44 PM, Dan <get...@gmail.com> wrote:

F(a,b) = floor(Int,a/b)*b

Ok, that's a good answer then.

[Sisyphuss]

Thanks, that seems to be a good idea!