Maths with in Rails

Rails
1

Hi All

I have a idea that I am doing and it is working so far but when it
comes to displaying the data that I am getting
with the maths that I am doing I am not getting the same result.

This is what I have

@arrived = @worksheet.time_arrived_customer
@left = @worksheet.time_left_office

@left_cust = @worksheet.time_left_customer

@travel = ((@arrived - @left) * 2)
@worked = (@left_cust - @arrived)

@total = (@travel + @worked) / 60

So what I did was in the DB I am saving the hours in their minute
form.

08:00 = 480 min
08:15 = 495 min

And so on.

I am 100% sure the maths is working as I firstly did it on paper and
took those steps and put them into the action.

When it comes to the display I am superpose to get 2.75 but I only see
2 why is that

I have looked at number_with_precision but rather then getting 2.75 I
get 2.00

Any Ideas would be appreciated.

Regards

2

On Sep 8, 9:37am, Eugene de Winnaar [email protected] wrote:

I am 100% sure the maths is working as I firstly did it on paper and
took those steps and put them into the action.

When it comes to the display I am superpose to get 2.75 but I only see
2 why is that

by default if you are working with integers you’ll always get integers
back (by truncation). If you want floating point numbers then you
should convert the numbers you’re working with to floating point
numbers first (using to_f), so

5 /2 will always return 2, but 5.0 / 2 will produce 2.5

I have looked at number_with_precision but rather then getting 2.75 I
get 2.00

number_with_precision is for formatting a number, you still need to
actually have a number with the floating point component.

Fred

3

Without the code used in the display action it’s difficult to know
what’s going on but I’d guess you’re using an integer at some point
and that causes loss of precision.

4

Frederick C. wrote in post #1020782:

by default if you are working with integers you’ll always get integers
back (by truncation). If you want floating point numbers then you
should convert the numbers you’re working with to floating point
numbers first (using to_f), so

5 /2 will always return 2, but 5.0 / 2 will produce 2.5

This might also help to clarify what’s happening:

$ irb
ruby-1.9.2-p290 :014 > x = 5
=> 5
ruby-1.9.2-p290 :015 > y = 3
=> 3
ruby-1.9.2-p290 :016 > z = x / y
=> 1
ruby-1.9.2-p290 :017 > x.class
=> Fixnum
ruby-1.9.2-p290 :018 > y.class
=> Fixnum
ruby-1.9.2-p290 :019 > z.class
=> Fixnum
ruby-1.9.2-p290 :020 > x = 5
=> 5
ruby-1.9.2-p290 :021 > y = 3.0
=> 3.0
ruby-1.9.2-p290 :022 > z = x / y
=> 1.6666666666666667
ruby-1.9.2-p290 :023 > x.class
=> Fixnum
ruby-1.9.2-p290 :024 > y.class
=> Float
ruby-1.9.2-p290 :025 > z.class
=> Float
ruby-1.9.2-p290 :026 > x = 5
=> 5
ruby-1.9.2-p290 :027 > y = 3
=> 3
ruby-1.9.2-p290 :028 > z = x.fdiv(y)
=> 1.6666666666666667
ruby-1.9.2-p290 :029 > x.class
=> Fixnum
ruby-1.9.2-p290 :030 > y.class
=> Fixnum
ruby-1.9.2-p290 :031 > z.class
=> Float
ruby-1.9.2-p290 :032 > z = x.quo(y)
=> (5/3)
ruby-1.9.2-p290 :033 > z.class
=> Rational
ruby-1.9.2-p290 :034 > z.to_f
=> 1.6666666666666667
ruby-1.9.2-p290 :035 > z.to_i
=> 1