# FloatDomainError while rounding

I am Trying to Round a number in my code which is as follows

param :a, 2, 5
param :b, 10, 49
param :extra1, 0, 3
@extra2 = @extra1 == 0 ? (1…3).choose : 0
@extra = [@extra1 , @extra2]
@coeff = []
(@extra.size).times{|i| @coeff[i] = @extra[i] == 0 ? (2…3).choose : 1 }
@num = @extra.last==0 ?
@extra.sumMath::log10(@a):@extra.sumMath::log10(@b)

@den1 = @coeff.first * Math::log10(@a)
@den2 = @coeff.last * Math::log10(@b)

@answer = @extra.last == 0 ? (-1*@num)/(@den1-@den2) :
(@num)/(@den1-@den2)

And I am facing an " ‘round’: Infinity (FloatDomainError)". How can I
fix it.

Thanks for any Hints.
Raj

On Tue, Sep 18, 2012 at 2:04 PM, raj g. [email protected] wrote:

@num = @extra.last==0 ?

And I am facing an " ‘round’: Infinity (FloatDomainError)". How can I
fix it.

Can you print @den1 and @den2 after setting them? If they are equal,
then the divisor will be 0, hence the Infinity error.

1.9.2p290 :023 > a = 1.0/0
=> Infinity
1.9.2p290 :024 > (a * 100).round
FloatDomainError: Infinity
from (irb):24:in `round’

Jesus.

Yes I have printed @den1 and @den2 but both of them are not same. even
than I face the same problem when I tried to round @answer.

If I print @answer without rounding I am not getting the error and
getting a Number with long floating point Which is not required for me.

Raj

On Tue, Sep 18, 2012 at 4:23 PM, raj g. [email protected] wrote:

Yes I have printed @den1 and @den2 but both of them are not same. even
than I face the same problem when I tried to round @answer.

If I print @answer without rounding I am not getting the error and
getting a Number with long floating point Which is not required for me.

OK. Let’s simplify. Can you show the minimal piece of code that
produces the error. Like:

a = ?
b = ?
coeff = [?,?]
num = ?

den1 = coeff.first * Math::log10(a)
den2 = coeff.last * Math::log10(b)
p den1
p den2

Can you assign some example values to the variables (where I placed
the ?) from your program, run this and show us the output?
BTW, I’m not sure you need instance variables (variables starting with
@). Unless you are actually inside an instance of a class and you need
to keep all those values around.

Jesus.

On 18.09.2012 16:51, Alex G. wrote:

Raj

In that case @num must be Infinity (or -Infinity). Possibly @a or @b
are 0 and so the logarithms you are calling earlier generate
-Infinity. Either way, as Jesus says the simplest thing is to just
print out all the intermediate variables until you see what’s wrong.

number is above the Float maximum limit it will also die with this error
(so not necessarily Infinity, but a large number):

(Float::MAX_10_EXP).round
=> 308

(1E308).round
=>
100000000000000001097906362944045541740492309677311846336810682903157585404911491537163328978494688899061249669721172515611590283743140088328307009198146046031271664502933027185697489699588559043338384466165001178426897626212945177628091195786707458122783970171784415105291802893207873272974885715430223118336

(1E309).round
(irb):23: warning: Float 1E309 out of range
FloatDomainError: Infinity
from (irb):23:in `round’
from (irb):23

On 18.09.2012 15:23, raj g. wrote:

Yes I have printed @den1 and @den2 but both of them are not same.
even
than I face the same problem when I tried to round @answer.

If I print @answer without rounding I am not getting the error and
getting a Number with long floating point Which is not required for
me.

Raj

In that case @num must be Infinity (or -Infinity). Possibly @a or @b
are 0 and so the logarithms you are calling earlier generate -Infinity.
Either way, as Jesus says the simplest thing is to just print out all
the intermediate variables until you see what’s wrong.

On 20.09.2012 05:04, raj g. wrote:

any solution for this to avoid this FloatDoaminError?
Are you really sure that such a large number is the correct output from

If so, then AFAIK your only option is to use BigDecimal in your
calculations rather than Float:

Hi Alex,

Thanks for that I’ll definitely try it out.

Raj

Alex G. wrote in post #1076502:

On 18.09.2012 16:51, Alex G. wrote:

Raj

In that case @num must be Infinity (or -Infinity). Possibly @a or @b
are 0 and so the logarithms you are calling earlier generate
-Infinity. Either way, as Jesus says the simplest thing is to just
print out all the intermediate variables until you see what’s wrong.

number is above the Float maximum limit it will also die with this error
(so not necessarily Infinity, but a large number):

(Float::MAX_10_EXP).round
=> 308

(1E308).round
=>

100000000000000001097906362944045541740492309677311846336810682903157585404911491537163328978494688899061249669721172515611590283743140088328307009198146046031271664502933027185697489699588559043338384466165001178426897626212945177628091195786707458122783970171784415105291802893207873272974885715430223118336

(1E309).round
(irb):23: warning: Float 1E309 out of range
FloatDomainError: Infinity
from (irb):23:in `round’
from (irb):23

Thanks for the explanation. So How can we avoid this problem? Is there
any solution for this to avoid this FloatDoaminError?