// recursive example

#include "ailib.h"

int count1(int ls){
	int s = 0;
	while( ls != NIL ){
		s++;
		ls = tail(ls);
	}
	return s;
}

int count2(int ls){
	if( ls == NIL ) return 0;
	return 1 + count2(tail(ls));
}

int count3(int ls){
	if( ls == NIL ) return 0;
	if( isatom(head(ls)) ) return 1 + count3(tail(ls));
	return count3(head(ls)) + count3(tail(ls));
}

int count4(int ls){
	if( ls == NIL ) return 0;
	if( isatom(ls) ) return 1;
	return count4(head(ls)) + count4(tail(ls));
}

int unum1(int n){
	int ls;
	ls = NIL;
	while(n > 0){
		ls = cons(number(1),ls);
		n--;
	}
	return ls;
}

int unum2(int n){
	if( n == 0 ) return NIL;
	return cons(number(1), unum2(n-1));
}

int cat2(int a, int b){
	if( a == NIL ) return b;
	return cat2( tail(a), cons(head(a),b) );
}

int uadd(int n, int m){
	if( m == NIL ) return n;
	if( n == NIL ) return m;
	return uadd( tail(n), cons(head(n),m) );
}

int usub(int n, int m){            // assume n >= m
	if( m == NIL ) return n;
	return usub( tail(n), tail(m) );
}

int reverse2(int ls, int ls1){
	if( ls == NIL ) return ls1;
	return reverse2(tail(ls), cons(head(ls),ls1));
}

int reverse(int ls){
	return reverse2(ls, NIL);
}

int main(void){
	int a, b, c;
	a = cons(number(2),cons(number(3),NIL));
	b = cons(number(1),list(a));
//	print_list(b);
//	printf("%d\n", cnt4(b));
	a = unum1(4);
//	b = unum2(3);
	c = cat2(a,b);
	c = uadd(a,b);
	c = usub(a,b);
	c = reverse(b);
	print_list(c);
}