title: haskell how to check two lists of tuples are equal and take union
body: <p>I am a new self-leaner in Haskell. firstly, I want to write a function to check if two lists of tuples are equal. Each tuple has a key and value</p>
  
  <p>secondly, I want a function to union two lists of tuples</p>
  
  <p>I tried several ways and tried many times but seems couldn't meet my requirements. could anyone help me? thanks in advance.</p>