From: yermej <yermej@...>
Date: 2007-11-23T15:10:03+09:00
Subject: Re: syntax Float equality within epsilon

On Nov 22, 10:16 pm, Phrogz <phr...@mac.com> wrote:
> On Nov 22, 1:38 am, unbewusst.s...@weltanschauung.com.invalid (Une
>
>
>
> Bévue) wrote:
> > i need to test float numbers within an epsilon, then i've extended the
> > Float clas like that :
>
> > class Float
> >   def ===( aFloat, eps = 1.0e-10)
> >     begin
> >       clazz = aFloat.class.to_s
> >       raise "Argument \"#{aFloat}\" must be a Float (being of
> > #{clazz})." if clazz != "Float"
> >       ( self > aFloat - eps ) && ( self < aFloat + eps )
> >     rescue
> >       puts "An error occurred: #{$!}"
> >       nil
> >     end
> >   end
> > end
>
> > this works as expected except when i want not to use the default value
> > for eps where i couldn't find the correct syntax :
> > a = 1.000000001
> > b = 1.00000000012
> > p ( a ===( b, 0.001) ).to_s
> > gave me :
> > [...] syntax error, unexpected ')', expecting tCOLON2 or '[' or '.'
> > p ( a ===( b, 0.001) ).to_s
> >                     ^
>
> > why ???
>
> Some operator methods have syntax sugar that prevents them from taking
> multiple arguments using simple syntax. You can get around this,
> albeit with a slightly less elegant syntax:
>
> irb(main):013:0> class Float
> irb(main):014:1>   def ===( a, b )
> irb(main):015:2>     p a, b
> irb(main):016:2>   end
> irb(main):017:1> end
> => nil
> irb(main):018:0> a = 5.4
> => 5.4
> irb(main):019:0> a.send( :===, 42, 73 )
> 42
> 73
> => nil
>
> If this is a case you'd use often, I suggest simply giving it a normal
> method name. that you can call without using #send

It can still be called without send. In place of a.send... in the
above example use:

a.===(42, 73)

Still not pretty, but a bit shorter.

Jeremy