OpenEuphoria

1. datetime:diff() question

• Posted by jessedavis Dec 08, 2017
• 1433 views

I think there is a problem with the documentation for datetime:diff()
From the euManual: 8.4.5.19 diff(dt1,dt2)

include std/datetime.e 
include std/console.e 
include std/os.e 
include std/convert.e 
 
datetime dt1 = datetime:now() 
sleep(2)  -- sleep for 2 seconds 
datetime dt2 = datetime:now() 
puts(1,"datetime dt1 = " & to_string(dt1) & 10) 
puts(1,"datetime dt2 = " & to_string(dt2) & 10) 
atom i = diff(dt1, dt2) -- i is 2 
--dt2 is subtracted from dt1  from euManual 8.4.5.19 diff 
printf(1,"i = %d\n",i) 
any_key("Done...") 

Now, if a bigger number is subtracted from a smaller number the difference is negative; however, according to the program output the difference is positive.

datetime dt1 = {2017,12,8,9,51,41} 
datetime dt2 = {2017,12,8,9,51,43} 
i = 2 
Done... 

3. Re: datetime:diff() question

• Posted by ghaberek (admin) Dec 08, 2017
• 1409 views

The manual says this:

But the code says this:

public function diff(datetime dt1, datetime dt2) 
    return datetimeToSeconds(dt2) - datetimeToSeconds(dt1) 
end function 

If I am indeed "subtracting dt2 from dt1" then I would write that as dt1 - dt2.

I am not sure which is supposed to be correct, the code or the manual.

-Greg

5. Re: datetime:diff() question

• Posted by _tom (admin) Dec 08, 2017
• 1372 views

From wikipedia I get:

minuend minus subtrahend equals difference 
 
4 - 6 = - 2   
 
(verbally, "four minus six equals negative two") 

same as: difference equals minuend minus subtrahend

as a function you would say ... difference( minuend, subtrahend )

diff( end_time, start_time ) 

_tom

7. Re: datetime:diff() question

• Posted by Ekhnat0n Dec 08, 2017
• 1381 views

It's all a matter of semantics (and logic) Neither manual nor sourcecode are wrong because they do not contradict each other

The problem is that jesse's vars dt1 and dt2 bear the same name as the arguments INSIDE the function diff(arg1, arg2), however, and if they had been named start and stop no misunderstanding would have risen.
If you are asked if val1 is lower or higher than val2, you will answer heigher in the case of TS.
Indicating a positive difference between them, but in order to achieve that, diff() must calculate arg2-arg1
to show that the 2nd is highest.
The scope of dt1 and dt2 inside diff() is limited to the function, and that's causing the problem for this particular case.

9. Re: datetime:diff() question

• Posted by Ekhnat0n Dec 08, 2017
• 1401 views

Hello mr davis,

If you were asked the difference between 3 and 8, what would be your answer?
Let me guess.... 5
If I am correct, you have DEDUCTED 3 from 8 as everybody would do.
However I would (maybe) have answered MINUS 5, because I deducted 8 from 3, using Reverse Polish Notation
Hence the function diff(a,b) does exactly what you yourself did.

Regards,

Antoine

Under the hood, this function almost certainly looks like

function diff(object a,b)
if a<b then return b-a
else return a-b
end

OR

function diff(object a,b) return ABS(a-b) end

BECAUSE for finding the difference you will have to deduct the lower value from the higher one, not the 2nd argument from the 1st

11. Re: datetime:diff() question

• Posted by Ekhnat0n Dec 08, 2017
• 1326 views

Hello Pete,

As I did not look up the commented code in the manual and you did you surely will be right here.
To be honest, I didn't even try it, as it gives me the answer I would expect under the circumstances.
The reason i didn't try is that ATM neither Eu nor Phix works for me under Ubuntu.
The installation of both seemed to be alright, but if I try to run (eg) example.ex in the terminal with Phix,
I get an errormessage "p not found" even though I cd-ed to the phix-dir and the example.ex resides there too.
This was one of several points I would appreciate to have your "trouble-shooting advice" on.

On other topics I would like to approach you for you will get a message on LinkedIn.
The email-address you can use to contact me is achnaton45@gmail.com.
Just a little game with numbers: I have my Bday today (born in '45) so at 3² - 2²*3 I turn 2³*3² (my kind of numerology ;)

Kind regards,

Antoine

13. Re: datetime:diff() question

• Posted by jessedavis Dec 09, 2017
• 1313 views

The DIFFERENCE(a,b) = abs(a-b), hence:
Difference(8,5) = Difference(5,8) = 3; It is the distance on the number line between the two.
However,
(5-8) = -3 and (8-5) = 3; the algebraic sum.

Again, the semantics aside, the documentation and the result should agree.

Thanks for your comments.
regards,
jd