Syntax Float equality within epsilon

ruby-talk
1

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 ???

···

--
Une Bévue

2

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

···

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 ???

3

Quoth Phrogz:

···

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

Or you could use "normal" method call notation:

  irb(main):009:0> a.===(32, 73)
  32
  73
  => nil

Regards,
--
Konrad Meyer <konrad@tylerc.org> http://konrad.sobertillnoon.com/

4

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

···

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

5

fine, thanks this works great to me !

···

yermej <yermej@gmail.com> wrote:

a.===(42, 73)

Still not pretty, but a bit shorter.

--
Une Bévue