Why? Blocks

[Julian Leviston]

Why can I not do this:

c = [1,2,3,4,5,6,6,7,8,10]
b = {|aVal| aVal / 5 == 0}
d = c.select(b)

I would like to store sections of code so I don't have to repeat
myself...

Julian.

 

[Jamis Buck]

Why can I not do this:

c = [1,2,3,4,5,6,6,7,8,10]
b = {|aVal| aVal / 5 == 0}
d = c.select(b)

I would like to store sections of code so I don't have to repeat
myself...

b = Proc.new {|aVal| aVal / 5 == 0}
d = c.select(&b)

- Jamis

 

[Joe Van Dyk]

On Sep 8, 2005, at 8:49 PM, Julian Leviston wrote:
=20

Why can I not do this:

c =3D [1,2,3,4,5,6,6,7,8,10]
b =3D {|aVal| aVal / 5 =3D=3D 0}
d =3D c.select(b)

I would like to store sections of code so I don't have to repeat
myself...

=20
b =3D Proc.new {|aVal| aVal / 5 =3D=3D 0}
d =3D c.select(&b)

What's the significance of '&b' vs 'b'?

 

[David A. Black]

Hi --

Why can I not do this:

c = [1,2,3,4,5,6,6,7,8,10]
b = {|aVal| aVal / 5 == 0}
d = c.select(b)

I would like to store sections of code so I don't have to repeat
myself...

b = Proc.new {|aVal| aVal / 5 == 0}
d = c.select(&b)

What's the significance of '&b' vs 'b'?

&b means that it's serving as the code block for this method call. b
means the Proc object is just a regular argument to the method.


David

 

[Bill Kelly]

What's the significance of '&b' vs 'b'?

It tells ruby that parameter is to take the place
of the block, rather than be passed as one of the
arguments to the method.



Regards,

Bill

 

[Brian Schröder]

Why can I not do this:

c =3D [1,2,3,4,5,6,6,7,8,10]
b =3D {|aVal| aVal / 5 =3D=3D 0}
d =3D c.select(b)

I would like to store sections of code so I don't have to repeat
myself...

b =3D Proc.new {|aVal| aVal / 5 =3D=3D 0}
d =3D c.select(&b)

=20
What's the significance of '&b' vs 'b'?
=20
=20

There is a similiarity between the star and the ampersand operator. A
star packs and unpacks arrays, while the ampersand packs and unpacks
code. E.g.

$ cat star-ampersand.rb
def another_method(a, b, c)
yielda=3D>a, :b =3D> b, :c =3D> c)
end

def take_block(*args, &block)
another_method(*args, &block)
end

take_block(1,2,3) do | hash | p hash end

$ ruby star-ampersand.rb
{:b=3D>2, :c=3D>3, :a=3D>1}

regards,

Brian


--=20
http://ruby.brian-schroeder.de/

Stringed instrument chords: http://chordlist.brian-schroeder.de/

 

[Julian Leviston]

You ROCK

Man THANNNNKKKSSSS

It's gonna take me a little bit of study to work out blocks, lambdas
and Proc objects! Far out.
But how awesome that Ruby can do that. Awesome! I'm like excited
as... Every time I come up against a new problem domain, I get
these awesome answers from these awesome people! {BIG VIRTUAL HUGS}
thanks guys.

Julian.

Why can I not do this:

c = [1,2,3,4,5,6,6,7,8,10]
b = {|aVal| aVal / 5 == 0}
d = c.select(b)

I would like to store sections of code so I don't have to repeat
myself...

b = Proc.new {|aVal| aVal / 5 == 0}
d = c.select(&b)

- Jamis