const Lexem *leftmost_child( const Lexem *t ) {
if ( t->type == Lexem::APPLY or t->type == Lexem::SELECT or t->type == Lexem::CHANGE_BEHAVIOR )
return leftmost_child( t->children[ 0] ); // a(15)
if ( t->type > 0 )
if ( ( t->num & 1 )/*need_left_arg*/ or ( ( t->num & 4 )/*MayNeedlarg*/ and t->children[0] ) )
return leftmost_child( t->children[ 0 ] ); // a', a-b
return t;
}
chooser::pitem chooser::delete_element(pitem p) {
pitem res = nullptr;
if (!p->L && !p->R) {
if (p->parent) {
res = p->parent;
if (is_left_child(p)) {
res->L = nullptr;
} else {
res->R = nullptr;
}
}
delete p;
} else if (!p->L || !p->R) {
if (p->parent) {
res = p->parent;
if (is_left_child(p)) {
res->L = p->L ? p->L : p->R;
} else {
res->R = p->L ? p->L : p->R;
}
p->L = p->R = nullptr;
delete p;
} else {
if (p->L) {
right_rotale(p);
} else {
left_rotale(p);
}
return delete_element(p);
}
} else {
pitem q = leftmost_child(p->R);
if (q != p->R) {
std::swap(p->L, q->L);
std::swap(p->R, q->R);
recalc(p);
recalc(q);
const pitem p_par = p->parent;
make_parent(q->parent, p);
make_parent(p_par, q);
} else {
left_rotale(p);
}
assert(!p->L || !p->R);
delete_element(p);
res = q->parent ? q->parent : q;
}
recalc(res);
return splay(res);
}
