Solution to Exercise 3.24

[clean99]

function make_table(same_key) {
    const local_table = list("*table*");
    function assoc(key, records) {
        return is_null(records)
               ? undefined
      	       : same_key(key, head(head(records)))
      	       ? head(records)
      	       : assoc(key, tail(records));
    }
    function lookup(key) {
        const record = assoc(key, tail(local_table));
        return is_undefined(record)
      	       ? undefined
      	       : tail(record);
    }
    function insert(key, value) {
        const record = assoc(key, tail(local_table));
        if(is_undefined(record)) {
               set_tail(local_table,
                        pair(pair(key, value), tail(local_table)));
            } else {
               set_tail(record, value);
            }
            return "ok";
    }
    function dispatch(m) {
        return m === "lookup"
               ? lookup
               : m === "insert"
               ? insert
               : error(m, "unknow operation -- table");
    }
    return dispatch;
}

const operation_table = make_table((a, b) => a === b);
const get = operation_table("lookup");
const put = operation_table("insert");