docs: def to_postfix(tokens):
      """
      Convert a list of evaluatable tokens to postfix format.
      """
      precedence = {
          '/': 4,
          '*': 4,
          '+': 3,
          '-': 3,
          '^': 2,
          '(': 1
      }
  
      postfix = []
      opstack = []
  
      for token in tokens:
          if is_int(token):
              postfix.append(int(token))
          elif is_float(token):
              postfix.append(float(token))
          elif token in mathwords.CONSTANTS:
              postfix.append(mathwords.CONSTANTS[token])
          elif is_unary(token):
              opstack.append(token)
          elif token == '(':
              opstack.append(token)
          elif token == ')':
              top_token = opstack.pop()
              while top_token != '(':
                  postfix.append(top_token)
                  top_token = opstack.pop()
          else:
              while (opstack != []) and (
                  precedence[opstack[-1]] >= precedence[token]
              ):
                  postfix.append(opstack.pop())
              opstack.append(token)
  
      while opstack != []:
          postfix.append(opstack.pop())
  
      return postfix