CISC 3142
Programming Paradigms in C++
Part II: Basic Facilities
Chapter 11 - Select Operations

Overview

Topics

Etc Operators

• i.e., operators that don't fit into any other standard categories

Logical Operators

• && and || short-circuit their operands
  • for && second operand is not evaluated if first is false
  • for || second operand is not evaluated if first is true

Conditional Expressions

• Remember, there must always be an 'else'/'false' (i.e., :) clause

  bool passed = average >= 60 ? true;  // compilation error -- no : clause
  		

  cout << a[i] << (i < n-1 ? ", "); // compilation error again … no false
  		

• Also, the type of the true/false clauses must be the same (or implicitly convertible)

  cout << a[i] << (i < n-1 ? ',' : ""); // compilation error true is char, false is string
  		

• Finally, keep in mind the low precedence of ?: (which is why the above example needed ()'s)

Increment and Decrement

• Reviewing the basic semantics of ++i and i++
  • pre-increment: value is incremented before using it as result of operation; i.e., ++i — the result of the expression is the new value of i

    i = i + 1;
    'return' i
    				

  • post-increment: value if incremented after using it as result of operation; i.e., i++ — the result of the expression is the old value of i

    hold = i
    i = i + 1;
    'return' hold
    				

Free Store

Arrays

• Arrays are created on the free store using syntax similar to Java:

  int *arr = new int[n];	// n already declared and initialized
  		

• When deleting an array allocated using new, one uses similar syntax:

  delete [] arr;
  		

  • This ensures that if the element is a class type with a destructor, the destructor is invoked for each element

Advice

Code Used in this Lecture