#!/usr/local/bin/python3
# Author: Dr. Robert Heckendorn, Computer Science Department, University of Idaho, 2013
import sys

# ensemble performance

# functionality of a symbol table:
# 1. make symbol table
# 2. length of symbol table 
# 2. list of keys
# 2. insert a new item by key
# 3. retrieve value based on key if not there return default
# 4. remove a specific item by key
# 5. sort the symbol table by the keys
# 6. join one symbol table to another
# 7. support duplicate keys with different information or only one copy?
#
# associative memory: LISP, Icon, Perl, Python
#


def makesymt() :
    return {}

def length(st) :
    return len(st)

def keys(st) :
    return st.keys()

def insert(st, key, value) :
    st[key] = value

def retrieve(st, key, default) :
    return st.get(key, default)

def remove(st, key) :
    if key in st :
        del(st[key])

def comparebykey(item) :
    return item[0]

def comparebyvalue(item) :
    return item[1]

def sortbykeys(st) :
    ans = list(st.items())
    ans.sort(key=comparebykey)
    return ans

def sortbyvalues(st) :
    ans = list(st.items())
    ans.sort(key=comparebyvalue)
    return ans
    
def join(st1, st2) :
    st1.update(st2)

def printsymbols(st) :
    syms = list(st.keys())
    syms.sort()
    for s in syms :
        print(s, st[s])