新手问题 array.flatten 怎么实现的
static VALUE rb_ary_flatten(int argc, VALUE *argv, VALUE ary) { int mod = 0, level = -1; VALUE result, lv;
rb_scan_args(argc, argv, "01", &lv); if (!NIL_P(lv)) level = NUM2INT(lv); if (level == 0) return ary_make_shared_copy(ary);
result = flatten(ary, level, &mod); OBJ_INFECT(result, ary);
return result; }
这段是从ruby-doc上贴的源码，感觉像是截出来的一部分，不是完整的。array.flatten 方法对于很深的嵌套好像都有效，这段源码好像没用到嵌套。
是完整的，重点是这行：result = flatten(ary, level, &mod);
flatten 方法的完整定义在这里 https://github.com/ruby/ruby/blob/eb15df1f894fa7235ccbcda7661f7d6a052045f6/array.c#L4508-L4564
static VALUE
flatten(VALUE ary, int level, int *modified)
{
long i = 0;
VALUE stack, result, tmp, elt;
st_table *memo;
st_data_t id;
stack = ary_new(0, ARY_DEFAULT_SIZE);
result = ary_new(0, RARRAY_LEN(ary));
memo = st_init_numtable();
st_insert(memo, (st_data_t)ary, (st_data_t)Qtrue);
*modified = 0;
while (1) {
while (i < RARRAY_LEN(ary)) {
elt = RARRAY_AREF(ary, i++);
if (level >= 0 && RARRAY_LEN(stack) / 2 >= level) {
rb_ary_push(result, elt);
continue;
}
tmp = rb_check_array_type(elt);
if (RBASIC(result)->klass) {
rb_raise(rb_eRuntimeError, "flatten reentered");
}
if (NIL_P(tmp)) {
rb_ary_push(result, elt);
}
else {
*modified = 1;
id = (st_data_t)tmp;
if (st_lookup(memo, id, 0)) {
st_free_table(memo);
rb_raise(rb_eArgError, "tried to flatten recursive array");
}
st_insert(memo, id, (st_data_t)Qtrue);
rb_ary_push(stack, ary);
rb_ary_push(stack, LONG2NUM(i));
ary = tmp;
i = 0;
}
}
if (RARRAY_LEN(stack) == 0) {
break;
}
id = (st_data_t)ary;
st_delete(memo, &id, 0);
tmp = rb_ary_pop(stack);
i = NUM2LONG(tmp);
ary = rb_ary_pop(stack);
}
st_free_table(memo);
RBASIC_SET_CLASS(result, rb_class_of(ary));
return result;
}