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Section 3.1 Worked Example: If Statements

Subgoals for Evaluating Selection Statements.

  1. Diagram which statements go together.

  2. For if-statement, determine whether expression is true or false.

  3. If true, follow true branch. If false, follow else branch (OR do nothing if there is no else branch).

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Given the following declarations:

int alpha = 2, beta = 1, delta = 3, eta = 0, gamma = 0;

double omega = 2.5, theta = -1.3, kappa = 3.0, lambda = 0.0, rho = 0.0;

Evaluate these statements and determine the value of all variables used.

if (kappa > omega)
   rho = kappa + 2;

Subsection 3.1.1 SG1: Diagram which statements go together.

If no { } are present, then by default all if and else branches have only a single statement:

if (kappa > omega)
   rho = kappa + 2;

Subsection 3.1.2 SG2: For if statement, determine whether true or false

First we evaluate (kappa > omega):

(3.0 > 2.5) is TRUE

Subsection 3.1.3 SG3: If true, follow true branch. If false, follow else branch (OR do nothing if there is no else branch).

The condition is TRUE so we execute the true branch:

rho = kappa + 2

= 3.0 + 2

= 5.0

Hint.

Answer: omega = 2.5, kappa = 3.0, rho = 5.0;

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