Design issues for functions

The following design issues are specific to functions:
  1. Are side effects allowed?
  2. What types of values can be returned?
  3. How many values can be returned?
1. Functional Side Effects: Because of the problems of side effects of functions that are called parameters to functions should always be in-mode (actual to formal parameter).
This requirement of in mode parameter passing prevents a function from causing side effects through its parameters.


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