How to Round off and Truncate in ruby

Ruby
1

Scenario.

I have an number x=12.45678

  1. I want a function to display x as a round of upto 3 decimal place as
    12.457
  2. Similarly truncate x at 3 decimal place as 12.456

I am using gsl library function and searched for TRUNC and ROUND
function but couldn’t find anything concrete

2

On Nov 20, 1:07 pm, Surjit N. [email protected]
wrote:

Scenario.

I have an number x=12.45678

  1. I want a function to display x as a round of upto 3 decimal place as
    12.457
  2. Similarly truncate x at 3 decimal place as 12.456
    irb(main):001:0> x=12.45678
    => 12.45678
    irb(main):002:0> s = “%.3f” % x
    => “12.457”
    irb(main):003:0> y = (x1000).round / 1000
    => 12
    irb(main):004:0> y = (x    1000).round / 1000.0
    => 12.457
    irb(main):007:0> class Numeric
    irb(main):008:1> def round_to( decimals=0 )
    irb(main):010:2> factor = 10.0**decimals
    irb(main):011:2> (self*factor).round / factor
    irb(main):012:2> end
    irb(main):013:1> end
    => nil
    irb(main):014:0> y = x.round_to(3)
    => 12.457
    irb(main):015:0> y = x.round_to(1)
    => 12.5
    irb(main):016:0> y = x.round_to(-1)
    => 10.0

Note that ‘rounding’ the number is subject to floating point precision
errors. Subsequent printing of a number rounded to 3 decimal places
like the above may display as something like 12.4569999999999999999

3

I am getting the truncate but the round off mentioned above doesn’t work

4

Surjit N. wrote:

I am getting the truncate but the round off mentioned above doesn’t work

Sorry… Its the opposite round of works but truncate doesn’t work

5

On Nov 20, 1:31 pm, Surjit N. [email protected]
wrote:

I am getting the truncate but the round off mentioned above doesn’t work

As shown above, it certainly does work. (You are looking at the actual
output of typing code directly into irb and having Ruby evaluate it.)

I assume your code is slightly different. Perhaps if pared it down to
a test case that showed exactly your problem, we could help further.

6

Surjit N. wrote:

Surjit N. wrote:

I am getting the truncate but the round off mentioned above doesn’t work

Sorry… Its the opposite round of works but truncate doesn’t work

Ah, I missed that you also wanted truncate.

irb(main):001:0> class Numeric
irb(main):002:1> # same potential floating point problem as round_to
irb(main):003:1* def truncate_to( decimals=0 )
irb(main):004:2> factor = 10.0**decimals
irb(main):005:2> (selffactor).floor / factor
irb(main):006:2> end
irb(main):007:1> end
=> nil
irb(main):008:0>
irb(main):009:0 x = 12.45678
=> 12.45678
irb(main):010:0> x.truncate_to( 3 )
=> 12.456
irb(main):011:0> x.to_s.sub /(.\d{3}).+/, ‘\1’
=> “12.456”

7

Surjit N. wrote:

I am getting the truncate but the round off mentioned above doesn’t work

Please share your test, e.g., http://tinyurl.com/24825g

Regards,