9B. Making Decisions in Expressions
(Optional)

Making choices in expressions

Expression a ? b : c  starts by evaluating expression a. If a is true (or nonzero), then a ? b : c  yields the value of expression b (and does not compute c at all). If a is false (or 0), a ? b : c  yields the value of expression c (and does not compute b at all). For example, int m = x > 0 ? x : -x; creates variable m and stores the absolute value of x into m. Only use this for expressions, not for statements. The coding standards require that.

Example: finding the larger of two numbers, version 3

// maximum(x,y) returns the larger of x and y. // If x and y are equal, it returns that shared value. // Examples: // maximum(1,5) = 5 // maximum(3,2) = 2 // maximum(4,4) = 4 int maximum(const int x, const int y) { return x > y ? x : y; }

Exercises

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1. Write a statement that makes m equal to 3n+1 if n is odd and to n/2 if n is even. Use a conditional expression. Answer