newbie question

[Will]

[Note: parts of this message were removed to make it a legal post.]

Greetings all, I think this is generally more a programming question than a
ruby explicit one, however, I am wondering why this code yields 23,
0.999999999999979 instead of 23, 1.

Any help would be great!

i = 0
while i <= 50
a = 37*i / 50
c = a + 0.0
b = (37*i/50.0 - c ) *50
if b < 1.5 && b > 0.5
puts i
puts b
end
i = i+1
end


thanks much
Will

 

[Farrel Lifson]

Rounding errors in floating point arithmetic.

Farrel

 

[Tim Hunter]

Greetings all, I think this is generally more a programming question than a
ruby explicit one, however, I am wondering why this code yields 23,
0.999999999999979 instead of 23, 1.

A common question. Check out http://en.wikipedia.org/wiki/Floating_point.

 

[Todd Benson]

Greetings all, I think this is generally more a programming question than a
ruby explicit one, however, I am wondering why this code yields 23,
0.999999999999979 instead of 23, 1.

Any help would be great!

i = 0
while i <= 50
a = 37*i / 50
c = a + 0.0
b = (37*i/50.0 - c ) *50
if b < 1.5 && b > 0.5
puts i
puts b
end
i = i+1
end

require 'bigdecimal'

#put a bigdecimal in the numerator or denominator...
((BigDecimal("37") * 23 / 50 - 17) * 50).to_f
#=> 1.0

Todd