Nested IF-ELSE statements:
The if-else statement is used to select between the two statements. In order to select from more than two statements, the if-else statements can also be nested, one inside of the other. For illustration, consider executing the following continuous mathematical function y = f(x):
y = 1 for x < -1
y = x^{2} for -1 ≤ x ≤ 2
y = 4 for x > 2
The value of y depends on the value of x that could be in one of three possible ranges. Selecting which range could be proficient with three separate if statements, which is as shown:
if x < -1
y = 1;
end
if x > = -1 && x < = 2
y = x^2;
end
if x > 2
y = 4;
end
As the three possibilities are mutually exclusive, then the value of y can be determined by using three individual if statements. Though, this is not very efficient code: all the three Boolean expressions should be computed, regardless of the range in which the x falls. For illustration, if x is less than -1, the initial expression is true and 1 would be assigned to y. Though, the two expressions in the next two if statements are still computed. Rather than of writing it in such a way, the expressions can be nested so that the statement ends whenever an expression is found to be true:
if x < -1
y = 1;
else
% If we are here, x must be > = -1
% Use an if-else statement to choose
% between the two remaining ranges
if x > = -1 && x < = 2
y = x^2;
else
% No need to check
% If we are here, x must be > 2
y = 4;
end
end