About variable name and method name

Ruby
1

class Array
def atoh
hash = Hash.new
if size % 2 != 0
raise “size must be odd”
end

 0.step(size-1,2) do |c| hash[self[c]] = self[c+1] end
 hash

end
end

For “size” in the code above, we know it’s a self.size method actually.
But how ruby differ it’s a variable or an instance method?

Thanks.

2

2010/1/21 Ruby N. [email protected]:

end
You are aware that there is Hash[] already, are you?

irb(main):004:0> a=%w{foo bar baz buz}
=> [“foo”, “bar”, “baz”, “buz”]
irb(main):005:0> Hash[*a]
=> {“foo”=>“bar”, “baz”=>“buz”}

Btw, you can shorten your method by using #each_slice. I would do it
like this:

irb(main):008:0> module Enumerable
irb(main):009:1> def to_hash
irb(main):010:2> h={}
irb(main):011:2> each_slice(2) {|k,v| raise “size must be odd” if
v.nil?;h[k]=v}
irb(main):012:2> h
irb(main):013:2> end
irb(main):014:1> end
=> nil
irb(main):015:0> a.to_hash
=> {“foo”=>“bar”, “baz”=>“buz”}
irb(main):016:0> a[0…-1].to_hash
RuntimeError: size must be odd
from (irb):11:in block in to_hash' from (irb):11:in each_slice’
from (irb):11:in to_hash' from (irb):16 from /opt/bin/irb19:12:in ’
irb(main):017:0>

Disadvantage: it is not as safe as your solution because it will
detect an error even for Arrays with even number of elements if any
value is nil.

Advantage: it works for all Enumerables.

Synthesis:

module Enumerable
def to_hash
h = {}
key = flag = nil

each do |val|
  if flag
    h[key] = val
  else
    key = val
  end
  flag = !flag
end

raise 'odd!' if flag
h

end
end

For “size” in the code above, we know it’s a self.size method actually.
But how ruby differ it’s a variable or an instance method?

As soon as Ruby has seen an assignment it assumes a local variable. Try
this:

ruby -e ‘def f;123;end;def g;p f;f=0;p f;end;g’

More details can be found here:
http://www.ruby-doc.org/docs/ProgrammingRuby/html/language.html#UO

Kind regards

robert