Ruby floating point behavior typical of other langs??

[bradjpeek]

The second edition of _The_Ruby_Way_ has an example similar to the
following:

irb(main):001:0> puts 'not equal' unless (3.2 - 2.0) == 1.2
not equal
=>nil

The point is to illustrate why you might want to use BigDecimal (i.e.
so 3.2 - 2.0 would in fact = 1.2).

require 'bigdecimal'
x = BigDecimal("3.2")
y = BigDecimal("2.0")
z = BigDecimal("1.2")
p x - y == z ? "equal" : "not equal" # prints "equal"

I'm fairly new to Ruby and don't do much programming, but when I saw
this example I was surprised that the default behavior is that 3.2 -
2.0 != 1.2

To me, this violates the "Principal of least surprise", but I guess it
isn't a big deal because I don't remember it being discussed in
Programming Ruby book (but it certainly may have been).

Do other languages work this way?

 

[Wilson Bilkovich]

The second edition of _The_Ruby_Way_ has an example similar to the
following:

irb(main):001:0> puts 'not equal' unless (3.2 - 2.0) == 1.2
not equal
=>nil

The point is to illustrate why you might want to use BigDecimal (i.e.
so 3.2 - 2.0 would in fact = 1.2).

require 'bigdecimal'
x = BigDecimal("3.2")
y = BigDecimal("2.0")
z = BigDecimal("1.2")
p x - y == z ? "equal" : "not equal" # prints "equal"

I'm fairly new to Ruby and don't do much programming, but when I saw
this example I was surprised that the default behavior is that 3.2 -
2.0 != 1.2

To me, this violates the "Principal of least surprise", but I guess it
isn't a big deal because I don't remember it being discussed in
Programming Ruby book (but it certainly may have been).

Do other languages work this way?

Yep. This is pretty standard.
This article is tolerable, but rambles a bit:
http://en.wikipedia.org/wiki/Floating_point

 

[William James]

Yep. This is pretty standard.
This article is tolerable, but rambles a bit:
http://en.wikipedia.org/wiki/Floating_point

There was a personal computer that had a language in ROM
that used binary-coded-decimal floating point.
Using that language, 3.2 - 2.0 yielded precisely 1.2.