adding and subtracting time

[Kenneth Brody]

On 1/10/2016 12:52 PM, James Flanagan via Filepro-list wrote:
> I am trying to identify the most elegant way to add and subtract time with user input in filepro.  The first example, where dummy ti is a 2 digit .0 variable, does not work properly.  The second example, by changing ti to an 8 digit hms variable does.  however, i do not want to have end users accidentally or otherwise screwing up the 00:00:00 sequence.  therefore, how can i prompt a user for a 2 digit number and ultimately get filepro to remove the respective number of minutes from my tm dummy variable.  Thank you very much in advance.

Use time math.  If "a-b" has both "a" and "b" as time fields, filePro does 
all the magic for you.

> ::ti(2,.0):
> ::input popup ti "Please enter how many minutes ago to start the downtime clock^A":
> ::tm=@tm-"00^A"{ti{"^A00":

Because the result of:

     "00:" { ti { ":00"

is not a time field.  It's just a string.  Subtracting a string from a time 
field is not the same as subtracting a time from a time field, even if that 
string "looks like" a time.  Basically, the above will always subtract zero 
from @TM.

> ::ti(8,hms):
> ::input popup ti "Please enter how many minutes ago to start the downtime clock^A" default "00^A00^A00":
> ::tm=@tm-ti:

Here, you're actually passing a time.

There are several ways to handle this.

You could put the "00:nn:00" into a time field:

   xx(8,hms) = "00:" { ti { ":00" ; tm = @tm - xx

Another option would be to convert your "00:nn:00" to a time:

   tm = @tm - doedit("00:"{ti{":00","hms")

But, given that you are trying to subtract minutes from the time, simply 
divide the number of minutes by "60", to convert it to hours, and subtract that:

   tm = @tm - ti/"60"

Finally, since you're dealing with "clock" time, I would suggest using 
"time" rather than "hms".  The difference is that "time" will wrap at 
midnight.  Subtracting 30 minutes from 12:15AM ("00:15:00") as "hms" will 
give you negative 15 minutes("-0:15:00"), whereas using "time" will give you 
11:45pm ("23:45:00").

-- 
Kenneth Brody