Array.new(size=0, obj=nil)
Array.new(array)
Array.new(size) {|index| block }

Returns a new array. In the first form, the new array is

empty. In the second it is created with _size_ copies of _obj_
(that is, _size_ references to the same
_obj_). The third form creates a copy of the array
passed as a parameter (the array is generated by calling
to_ary  on the parameter). In the last form, an array
of the given size is created. Each element in this array is
calculated by passing the element's index to the given block and
storing the return value.

   Array.new
   Array.new(2)
   Array.new(5, "A")

only one copy of the object is created

a = Array.new(2, Hash.new)
a[0]['cat'] = 'feline'
a
a[1]['cat'] = 'Felix'
a

here multiple copies are created

a = Array.new(2) { Hash.new }
a[0]['cat'] = 'feline'
a

squares = Array.new(5) {|i| i*i}
squares

copy = Array.new(squares)

Source Code

/*
*  call-seq:
*     Array.new(size=0, obj=nil)
*     Array.new(array)
*     Array.new(size) {|index| block }
*
*  Returns a new array. In the first form, the new array is
*  empty. In the second it is created with _size_ copies of _obj_
*  (that is, _size_ references to the same
*  _obj_). The third form creates a copy of the array
*  passed as a parameter (the array is generated by calling
*  to_ary  on the parameter). In the last form, an array
*  of the given size is created. Each element in this array is
*  calculated by passing the element's index to the given block and
*  storing the return value.
*
*     Array.new
*     Array.new(2)
*     Array.new(5, "A")
* 
*     # only one copy of the object is created
*     a = Array.new(2, Hash.new)
*     a[0]['cat'] = 'feline'
*     a
*     a[1]['cat'] = 'Felix'
*     a
* 
*     # here multiple copies are created
*     a = Array.new(2) { Hash.new }
*     a[0]['cat'] = 'feline'
*     a
* 
*     squares = Array.new(5) {|i| i*i}
*     squares
* 
*     copy = Array.new(squares)
*/

static VALUE
rb_ary_initialize(argc, argv, ary)
   int argc;
   VALUE *argv;
   VALUE ary;
{
   long len;
   VALUE size, val;

   rb_ary_modify(ary);
   if (rb_scan_args(argc, argv, "02", &size, &val) == 0) {
       RARRAY(ary)->len = 0;
       if (rb_block_given_p()) {
           rb_warning("given block not used");
       }
       return ary;
   }

   if (argc == 1 && !FIXNUM_P(size)) {
       val = rb_check_array_type(size);
       if (!NIL_P(val)) {
           rb_ary_replace(ary, val);
           return ary;
       }
   }

   len = NUM2LONG(size);
   if (len < 0) {
       rb_raise(rb_eArgError, "negative array size");
   }
   if (len > 0 && len * (long)sizeof(VALUE) <= len) {
       rb_raise(rb_eArgError, "array size too big");
   }
   if (len > RARRAY(ary)->aux.capa) {
       REALLOC_N(RARRAY(ary)->ptr, VALUE, len);
       RARRAY(ary)->aux.capa = len;
   }
   if (rb_block_given_p()) {
       long i;

       if (argc == 2) {
           rb_warn("block supersedes default value argument");
       }
       for (i=0; i<len; i++) {
           rb_ary_store(ary, i, rb_yield(LONG2NUM(i)));
           RARRAY(ary)->len = i + 1;
       }
   }
   else {
       memfill(RARRAY(ary)->ptr, len, val);
       RARRAY(ary)->len = len;
   }

   return ary;
}