My Method of the Month lightning talk for the Columbus Ruby Brigade's September 2011 meeting.

1. NaN, Zero,
& Infinities
Methods of the Month from Ruby’s Float
Kevin Munc - @muncman
Monday, September 19, 2011

2. Numbers. Non-Numbers.
Monday, September 19, 2011

3. nan?
• True if the float is not a valid IEEE 754
floating point number.
• 0.0.nan? => false
• (0.0/0).nan? => true
• Float::NAN
Monday, September 19, 2011

4. nan?
• 0.0/0 => NaN
• This is in contrast to the
ZeroDivisionError that results when using
Fixnums to divide by zero.
Monday, September 19, 2011

5. Monday, September 19, 2011

6. Zero is worth something
Monday, September 19, 2011

7. zero?
• Only true for 0.0 or -0.0
• 0.0.zero? => true
• -0.0.zero? => true
• 0.0001.zero? => false
Monday, September 19, 2011

8. Tangent::Trivia
“The centre of York station was used as
the zero point for distance measurement
for much of the rail network in the North
East of England.” - http://www.flickr.com/photos/xerones/3887271255/
The lines, from the top:
1. Longlands Loop (Northallerton)
2. Market Weighton & Beverley
3. Micklefield Branch
4. Raskelf Curve
5. Sherburn Branch
6. York & Harrogate
7. York & Market Weighton
8. York & Newcastle
9. York & North Midland
10. York & Scarborough
Monday, September 19, 2011

9. infinite? finite?
Monday, September 19, 2011

10. finite?
• True if the float is a valid IEEE floating point
number; true if not Infinity and not NaN.
• 1.0.finite? => true
• 0.0.finite? => true
• (0.0/0).finite? => false (NaN)
• (1.0/0).finite? => false (Infinity)
Monday, September 19, 2011

11. Infinity is a little weird
Monday, September 19, 2011

12. infinite?
• Returns nil if float is finite
• Returns nil if float is NaN
• Returns -1 if float is -infinity
• Returns +1 if float is +infinity
Monday, September 19, 2011

13. infinite?
• (0.0).infinite? => nil (finite)
• (0.0/0).infinite? => nil (NaN)
• (1.0/0).infinite? => 1
• (-1.0/0).infinite? => -1
Monday, September 19, 2011

14. infinite?
• (1.0/0) => Infinity
• (-1.0/0) => -Infinity
• Float::INFINITY
Monday, September 19, 2011

15. infinite?
• Float::INFINITY + 100 => Infinity
• Float::INFINITY - 100 => Infinity
• Float::INFINITY * Float::INFINITY => Infinity
• Float::INFINITY == Float::INFINITY => true
Monday, September 19, 2011

16. infinite?
• Float::INFINITY == (1.0/0) => true
• Float::INFINITY == (-1.0/0) => false
• Float::INFINITY - Float::INFINITY => NaN
Monday, September 19, 2011

17. Uses for Infinity?
• Range?
• everything = -Infinity..Infinity
• Versus Float::MAX ?
• To represent something completely
unbounded?
• Others?
Monday, September 19, 2011

18. questions.zero?
Photo Credits
• http://www.flickr.com/photos/shanedk/3959630757/
• http://www.flickr.com/photos/cogdog/3160739508/
• http://www.flickr.com/photos/shyald/3182510815/
• http://www.flickr.com/photos/affers/3183414031/
• http://www.flickr.com/photos/doug88888/4542924531/
• http://www.flickr.com/photos/libraryman/12835119/
• http://www.flickr.com/photos/xerones/3887271255/
• http://www.flickr.com/photos/jcolman/334602926/
Monday, September 19, 2011