Key for Homework 6 on Scope and Parameters

 Q  A   Reason
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For questions 1 through 5 you need to remember the basic rules for scope:

  - The scope of an identifier begins where the declaration occurs.
  - The scope extends to the end of the block, if any, in which the declaration
    occurs.
  - The scope of a formal parameter is the body of the function.
  - "Local" names declared within a block hide declarations of the same name in
    an enclosing block.
    
 1  5   Straight from the rules.
 2  5   Straight from the rules.
 3  5   Straight from the rules.
 4  1   Straight from the rules.
 5  9   

 6  2   For this to compile, Alpha must be declared somewhere that would put it
        in scope within the body of the function Calc().  Since there's no local
        declaration for Alpha, the only alternative is that it must be declared
        at file (or global) scope.
        
 7  1   The function receives a copy of the actual parameter, placed in the
        corresponding formal parameter.  So, there's no way for the function to
        modify the actual parameter.  Since a copy is passed, the actual parameter
        could be a variable or a constant or an expression.
        
 8  6   The formal parameter is an alias for the actual parameter, so any change
        to the formal parameter will also change the actual parameter.  When
        pass-by-reference is used, the actual parameter MUST be a variable.
        
 9  5   Same situation as in question 8, except that the const means that the
        function is not allowed to modify the formal parameter, so it can't make
        any changes to the actual parameter.
        
10  3   Since the data flow for alpha is one-way into the function, it should be
        passed by value (the function does not need to change the actual parameter).
        
        Since the data flow for beta is two-way, the function needs to modify the
        actual parameter, so beta must be passed by reference.
        
        alpha could also be passed by constant reference, but that's not a choice
        in the given answers.