ruby - Is it possible to alter an Array object's length? -

February 15, 2011

how 1 alter self in array totally new array? how fill in commented portion below?

class array   def change_self     #make array `[5,5,5]`   end end

i understand this: why can't change value of self? , know can't assign self new object. when do:

arr = [1,2,3,4,5]

arr contains reference array object. can add method array class alters array, like:

 self[0] = 100

but possible change length of array referenced arr? how these values stored in array object?

you asking 3 different questions in title , in text:

is possible alter array object's length using array method?

yes, there 20 methods can (potentially) change length of array:

<< increases length 1
[]= can alter length arbitrarily, depending on arguments
clear sets length 0
compact! can decrease length, depending on contents
concat can increase length, depending on arguments
delete can decrease length, depending on arguments , contents
delete_at can decrease length, depending on arguments
delete_if / reject! can decrease length, depending on arguments , contents
fill can increase length, depending on arguments
insert increases length
keep_if / select! can decrease length, depending on arguments , contents
pop decreases length
push increases length
replace can alter length arbitrarily, depending on arguments , contents (it replaces array different array)
shift decreases length
slice! decreases length
uniq! can decrease length, depending on contents
unshift increases length

when monkey patching array class, how 1 alter "self" totally new array? how fill in commented portion below?
class array  def change_self    #make array [5,5,5] no matter  end end 

class array   def change_self     replace([5, 5, 5])   end end

how these values stored in array object?

we don't know. ruby language specification not prescribe particular storage mechanism or implementation strategy. implementors free implement arrays way like, long obey contracts of array methods.

as example, here's array implementation in rubinius, find readable (at least more yarv):

vm/builtin/array.cpp: core methods , data structures
kernel/bootstrap/array.rb: minimal implementation bootstrapping rubinius kernel
kernel/common/array.rb: bulk of implementation

for comparison, here topaz's implementation: