How is this possible ?

Didier Bur

Hi,
While working on a new version of the compoSpray script, I've comme across that: select a 2D "faceme" component and:

c=Sketchup.active_model.selection[0].definition
#<Sketchup;;ComponentDefinition;0xc3f3cf0>
c.bounds.height
9.09494701772928e-013
c.bounds.height < 0.001 returns false !
c.bounds.height == 0.001 returns true !

Where am I missing something, or is Ruby crazy ?

thomthom

SketchUp's internal accuracy is 1000 of an inch. So any lengths you compare that are shorter than that - or when the difference between the lengths is less than 0.001 - will compare as equal.

Length.<
http://code.google.com/apis/sketchup/docs/ourdoc/length.html

@unknownuser said:

The < method is used to see if one length is less than another length.
For example, if l1 = 1.0.inch and l2 = 1.000001.inch then l1 == l2 so l1 < l2 should return false.

thomthom

hm... am I making stuff up again...

Didier Bur

Thanks thomthom,
and while we are at it, another weird thing:

def test()
case Sketchup.active_model.selection[0].class
		  when Sketchup;;Face
			puts "face"
		  when Sketchup;;ComponentInstance
			puts "instance"
		  when Sketchup;;Group
			puts "group"
		  when Sketchup;;Image
			puts "image"
		  when Sketchup;;Edge
			puts "edge"
		  else
			puts "something else"
		end
end

This always outputs "something else" in the Console. Case with 'class' as switch isn't allowed or not effective ?

TIG

This comparison weirdness doesn't happen for me.
Do you have a script that's loading and resetting == for 'equality comparisons' in the Float class?
I ran a BareGrep on my ../Plugins folder and found no likely culprits for ' class Float' matches - although I did find I have a Float def =~ in my Roof.rb tools which takes Floats to within 1/1000 as being equal - as in 0.0001==0 >>> false BUT 0.0001=~0 >>> true - but I don't suspect that...
This is what I get

y=9.09494701772928e-013
9.09494701772928e-013
y==0
false
y<0
false
y>0
true
y==0.001
false
y>0.001
false
y<0.001
true
(y*1000000).to_i/1000000.0
0.0
(y*10000000000000).to_i/10000000000000.0
9.0e-013

So you can see how to test for nearness to zero with the differing accuracies as the last two examples...
BUT all == return correct results otherwise

TIG

@didier bur said:

Thanks thomthom,
and while we are at it, another weird thing:

def test()
> case Sketchup.active_model.selection[0].class
> 		  when Sketchup;;Face
> 			puts "face"
> 		  when Sketchup;;ComponentInstance
> 			puts "instance"
> 		  when Sketchup;;Group
> 			puts "group"
> 		  when Sketchup;;Image
> 			puts "image"
> 		  when Sketchup;;Edge
> 			puts "edge"
> 		  else
> 			puts "something else"
> 		end
> end

This always outputs "something else" in the Console. Case with 'class' as switch isn't allowed or not effective ?

I found this out when writing my SKMtools class

case v.class.to_s
  when 'Fixnum'

was my fix... it returns the class name as a string and compares it with another string in the 'when'... so your method WILL work thus

    def test()
    case Sketchup.active_model.selection[0].class.to_s
            when 'Sketchup;;Face'
             puts "face"
            when 'Sketchup;;ComponentInstance'
             puts "instance"
            when 'Sketchup;;Group'
             puts "group"
            when 'Sketchup;;Image'
             puts "image"
            when 'Sketchup;;Edge'
             puts "edge"
            else
             puts "something else"
          end
    end

thomthom

@tig said:

This comparison weirdness doesn't happen for me.
Do you have a script that's loading and resetting == for 'equality comparisons' in the Float class?

The object type you get from Boundingbox is Length - not Float. This is why you see this difference. Length has that tolerance built in. Something one need to be aware of when you compare data in Ruby SU. Always check if you have a Float or Length.

@tig said:

was my fix... it returns the class name as a string and compares it with another string in the 'when'... so your method WILL work thus

But will be very slow - same performance issue like using .typename.

I don't know why one can't use class for switch cases - but instead you should use if,elsif along with .class or .is_? in order to maintain performance. As string operations while iterating entities is just all too big of an performance hit.

Didier Bur

Thanks tt & tig for yur answers;
I'm aware of the "strings comparison time killer" that's why i want to use the class for the switch.
i'll use "elseif" instead

thomthom

I really don't understand why switch own't work - since face1.class == face2.class work fine...

thomthom

Ah - so then we can just do this:


def test()
case Sketchup.active_model.selection[0]
        when Sketchup;;Face
         puts "face"
        when Sketchup;;ComponentInstance
         puts "instance"
        when Sketchup;;Group
         puts "group"
        when Sketchup;;Image
         puts "image"
        when Sketchup;;Edge
         puts "edge"
        else
         puts "something else"
      end
end

Right?

Didier Bur

Partial answer here: http://www.postal-code.com/mrhappy/blog/2007/02/01/ruby-comparing-an-objects-class-in-a-case-statement/
and here http://groups.google.com/group/comp.lang.ruby/browse_thread/thread/3d83faf049160e58

This works:

case Sketchup.active_model.selection[0]
            when 'Sketchup;;Face'
             puts "face"
...

The simplest the best !

TIG

@didier bur said:

Partial answer here: http://www.postal-code.com/mrhappy/blog/2007/02/01/ruby-comparing-an-objects-class-in-a-case-statement/
and here http://groups.google.com/group/comp.lang.ruby/browse_thread/thread/3d83faf049160e58

This works:

case Sketchup.active_model.selection[0]
>             when 'Sketchup;;Face'
>              puts "face"
> ...

The simplest the best !

So in your case

    def test()
    case Sketchup.active_model.selection[0]
            when Sketchup;;Face
             puts "face"
            when Sketchup;;ComponentInstance
             puts "instance"
            when Sketchup;;Group
             puts "group"
            when Sketchup;;Image
             puts "image"
            when Sketchup;;Edge
             puts "edge"
            else
             puts "something else"
          end
    end

should work ??? Avoiding the .to_s step