Is there a method to set variable to NaN or Infinity?

Ruby
1

Is there a built-in method to set a floating point value to NaN or
Infinity? Or, is the only way to do this by

a = 0.0/0.0 # set a to NaN

b = 3.0/0.0 # set b to Infinity

c = -3.0/0.0 # set c to -Infinity

Also, how can I set value to -NaN? This is possible in other languages,
but I can’t do it in Ruby. I’ve tried:

a = 0.0/0.0

b = -a

but b still comes out NaN.

–Alex

2

I read in the BigDecimal docs you can do n = BigDecimal.new(‘NaN’). But
i’m unfamiliar with it

On Thu, Apr 1, 2010 at 3:57 PM, Alex DeCaria

3

On Thu, Apr 1, 2010 at 3:57 PM, Alex DeCaria
[email protected] wrote:

Is there a built-in method to set a floating point value to NaN or
Infinity? Or, is the only way to do this by
a = 0.0/0.0 # set a to NaN
b = 3.0/0.0 # set b to Infinity
c = -3.0/0.0 # set c to -Infinity

In the past I have done something like:
Float::NaN = 0.0 / 0.0 #=> NaN
Float::Infinity = 3.0 / 1.0 #=> Infinity
-Float::Infinity #=> -Infinity
In other words, do they have to be methods? Can they just be constants?
(But I think it might be useful to have those constants automatically in
Float?)

Also, how can I set value to -NaN? This is possible in other languages,
but I can’t do it in Ruby. I’ve tried:
a = 0.0/0.0
b = -a
but b still comes out NaN.

I’m curious: which languages have a -NaN value and why would you want
to use it instead of just NaN?
I’ve just tried Octave, and in that
n = 0.0 / 0.0 #=> NaN
nn = -n #=> NaN
so I assume that there isn’t a “-NaN” in Octave, although as Nan ==
NaN returns 0 (false)
I’d need to look at the documentation to be sure.

Colin B.

4

I’m curious: which languages have a -NaN value and why would you want
to use it instead of just NaN?

I do a lot of my scientific programming in IDL. It allows explicit
assignment of NaN and -NaN to floating point variables, as well as
returns -NaN under certain circumstances. IDL is used for a lot of
image processing, and being able to have NaN and/or -NaN is useful as a
mask when processing the arrays.

–Alex

5

On Apr 1, 2010, at 3:48 PM, Colin B. wrote:

Float::Infinity = 3.0 / 1.0 #=> Infinity
That’s a pretty small infinity :slight_smile:

Mike

I’m curious: which languages have a -NaN value and why would you want
to use it instead of just NaN?
I’ve just tried Octave, and in that
n = 0.0 / 0.0 #=> NaN
nn = -n #=> NaN
so I assume that there isn’t a “-NaN” in Octave, although as Nan ==
NaN returns 0 (false)
I’d need to look at the documentation to be sure.

Colin B.

–

Mike S. [email protected]
http://www.stok.ca/~mike/

The “`Stok’ disclaimers” apply.

6

On Thu, Apr 1, 2010 at 10:21 PM, Mike S. [email protected] wrote:

On Apr 1, 2010, at 3:48 PM, Colin B. wrote:

In the past I have done something like:
Float::NaN = 0.0 / 0.0 #=> NaN
Float::Infinity = 3.0 / 1.0 #=> Infinity

That’s a pretty small infinity :slight_smile:

Mike

Well, us wot have studied maffematics can deal with LOADS of infinitys!
Or, in other words, oops!
Yes that should have been
Float::Infinity = 3.0 / 0.0 #=> Infinity

Alex DeCaria to ruby-talk wrote:

I’m curious: which languages have a -NaN value and why would you want
to use it instead of just NaN?
I do a lot of my scientific programming in IDL. It allows explicit
assignment of NaN and -NaN to floating point variables, as well as
returns -NaN under certain circumstances. IDL is used for a lot of
image processing, and being able to have NaN and/or -NaN is useful as a
mask when processing the arrays.

Fair enough!
As far as I know, Ruby uses “standard” floating point (so no negative
or “signed” NaN?), but I think we now need an answer from an expert.

Colin B.