From: flebber <flebber.crue@...>
Date: 2010-11-04T19:40:14+09:00
Subject: Re: Ruby Time - Sports Time

On Nov 4, 8:11 pm, Robert Klemme <shortcut...@googlemail.com> wrote:
> On Thu, Nov 4, 2010 at 8:50 AM, flebber <flebber.c...@gmail.com> wrote:
> > Hi I am reading the time classes for Ruby. However I can't figure out
> > what time method would be best for sports times. I am referring to
> > this linkhttp://www.ruby.ch/ProgrammingRuby/htmlC/ref_c_time.html
>
> > I want the times stored to be in a mm:ss:hh format or ss:hh (where hh
> > = hundreths of seconds).
>
> First we should distinguish between storage and representation.  You
> may want to print (i.e. use a representation) times in the format you
> give but that does not necessarily mean that you also want or need to
> store them that way.
>
> > The times stored will be of times occuring over distance, and some
> > will be imported from internet sources and some will come from direct
> > user input.
>
> > I am currently planning to use sequel and sqlite to store and query my
> > data.
>
> Second, it seems you want to store *durations* not *points in time*,
> which is what class Time is for.  For storing durations and doing the
> kind of math with them that you indicate it's best to base it on some
> numeric type, see below.
>
> > Any suggestions on the best and most reliable format? I forgot to
> > mention that sums and calculations including averages will be
> > performed on the times.
>
> I see two reasonable approaches:
>
> 1. Use what Time arithmetic provides (Floats)
>
> irb(main):011:0> t1=Time.now;sleep 1.2;t2=Time.now;t2 - t1
> => 1.205
>
> Then you would have to create a method duration_to_string(d) which
> creates the string representation that you want, e.g.
>
> def duration_to_string(d)
>   min,sec = d.divmod 60
>   sec,msec = sec.divmod 1
>   sprintf "%d:%02d:%03d", min, sec, msec * 1000
> end
>
> 2. Create a custom class Duration that contains a Float for the
> duration, implements all the math operators and which implemens #to_s
> with the code of duration_to_string above.
>
> Downside of this approach is that you then normally would want to
> change Time#+, Time#- etc. to return an instance of Duration and not
> Float to have it all nicely integrated.  With some effort you can get
> that done and probably also keep most code compatible.  That would be
> a nice experiment.
>
> You can find more info on approach 2 here:http://blog.rubybestpractices.com/posts/rklemme/019-Complete_Numeric_...
>
> Kind regards
>
> robert
>
> --
> remember.guy do |as, often| as.you_can - without endhttp://blog.rubybestpractices.com/

I have two questions regarding th numerical approaches.

> 1. Use what Time arithmetic provides (Floats)
> irb(main):011:0> t1=Time.now;sleep 1.2;t2=Time.now;t2 - t1
> => 1.205


This method minuses t1 - t2 to calculate duration. However the
duration will already be defined or imported. So to me this means that
I need to go down the second option of creating a class based on the
reverse of this.

> def duration_to_string(d)
>   min,sec = d.divmod 60
>   sec,msec = sec.divmod 1
>   sprintf "%d:%02d:%03d", min, sec, msec * 1000
> end

Can i clarify in the 2nd method what was meant by "implements all the
math operators". Every value would be positive as it is greater than
zero isn't it?