6th_Sept_data_structure_2

// lists from pair
// pair(data, pair(...)) - nested pair

//const denoms = pair(100,pair(50,pair(20,pair(10,5)));

//head(denoms); // 100 -> single elements
//tail(denoms);  // pair(50,pair(20,pair(10,5))) -> set of remaining elements 

// when denoms = (100,50)
// it should return 50 and set of elements

// => empty list : null 

const denoms = pair(100,
                    pair(50,
                        pair(20,
                            pair(10,
                                pair(5,
                                    null)))));
                                                
// a list is either a null or a pair whose tail is a list (recursive definition of list cause we are using list itself to define list)

const my_list = null;
const your_list = pair(8, null);
// null is a list

// evaluation of null in an if condition?


// retreiving data from the list:

head(denoms); // 100
head(tail(denoms)); // 50
head(tail(tail(denoms))); // 20
head(tail(tail(tail(denoms)))); // 10
head(tail(tail(tail(tail(denoms))))); // 5
tail(tail(tail(tail(tail(denoms))))); // null

// null is absence of value?