Help : a scoping question

A meta-programming question. More precisely a scoping problem.

In short, is there a ruby way to execute a parameter-less block with a
given receiver ?

Here below my example : I am manipulating a pattern of rectangular boxes
in a plane, with a tree structure given by enclosure, and want to
describe them by a convenient DSL. I am keeping some parameters from the
real code to give a flavor of the example.

class Box

HORIZ = 1
VERT = 2
FIXED = 4
ADJUST = 8

def initialize(enclosing, flag, columns = [], height = 0)
@enclosing = enclosing
enclosing << self if enclosing
@enclosed = []

end

def <<(other)
@enclosed << other
end

def box(params = {}, &block)
newbox = Box.new(self, params[:opts], params[:colums] || [],
params[:height] || 0)
block.call(newbox) if block
newbox
end

end # class box

duplication, part of the problem

def main_box(params ={}, &block)
newbox = Box.new(nil, params[:opts], params[:colums] || [],
params[:height] || 0)
block.call(newbox) if block
newbox
end

big_box = main_box :opts => VERT do |s|
s.box :opts => HORIZ, :colums => [1,2,3,4,5,6,7,8,9], :height => 10
s.box :opts => HORIZ do |b|
b.box :opts => VERT, :colums => [7,8,9], :height => 90
b.box :opts => VERT do |z|
z.box :opts => HORIZ | ADJUST, :colums => [1,2,3,4,5,6]
z.box :opts => HORIZ do |y|
y.box :opts => VERT | FIXED, :colums => [4,5,6], :height => 70
y.box :opts => VERT do |x|
x.box :opts => HORIZ| FIXED, :colums => [1,2,3], :height => 20
x.box :opts => HORIZ | ADJUST,:colums => [1,2,3]
x.box :opts => HORIZ | FIXED, :colums => [1,2,3], :height =>35
end
end
end
end
end

The local variables in the blocks could be all the same, and are useless
to the DSL, but they seem necessary to secure the scopes. My question is
: is there a way to write the method ‘box’ so that it accepts the
simplified DSL without variables :

… box params do
box params do

Apologies for my English.

Michel D.

Michel D. wrote:

In short, is there a ruby way to execute a parameter-less block with a
given receiver ?

pr = proc {p self}
2.instance_eval &pr
=> 2

Is that what you’re looking for?

Joel VanderWerf wrote:

Michel D. wrote:

In short, is there a ruby way to execute a parameter-less block with a
given receiver ?

pr = proc {p self}
2.instance_eval &pr
=> 2

Is that what you’re looking for?

Of course, you’re right : “newbox.instance_eval &block if block” works.
Many thanks !

M

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