MATLAB-BOOK Additional Flow Control: continue, break, return

Subsection Additional Flow Control: continue, break, return

MATLAB provides commands that modify normal loop flow. These are most often used inside an if-statement within a loop.

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Table 36. Flow control commands for loops

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Command	Effect
`continue`	Skip the rest of the current iteration and move to the next iteration.
`break`	Exit the loop immediately and continue after `end`.
`return`	Exit the current script or function immediately.

Important notes:

These commands only execute if MATLAB reaches the line where they appear.

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continue and break may only be used inside a for- or while-loop; using them elsewhere causes an error.

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return can be used anywhere inside a script or function to exit early.

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🌌 Example 37. Searching with break.

A loop can search for a target value and stop early when found. The break command exits the loop immediately.

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target = 10;

found = false;
location = -1;

for k = 1:50
    value = randi([-20 20]);   % generate one random integer

    if value == target
        found = true;
        location = k;
        break
    end
end

if found
    fprintf('The number %i was found on iteration %i\n', target, location)
else
    fprintf('The number %i was not found in 50 trials\n', target)
end

This pattern—test a condition, then exit early with break—is useful whenever you want to stop searching once you find what you need.

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🌌 Example 38. Example: Testing for Primality.

An integer greater than 1 is prime if it has no divisors other than 1 and itself. This loop tests potential divisors and stops early if it finds one:

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number = 75913;

if number < 2
	is_prime = false;
else
	divider = 2;
	is_prime = true;

	while divider <= sqrt(number)
		if mod(number, divider) == 0
			is_prime = false;
			break
		end
		divider = divider + 1;
	end
end

if is_prime
	fprintf('The number %0.10g is prime!\n', number)
else
	fprintf('The number %0.10g is not prime!\n', number)
end

We only need to test divisors up to \(\sqrt{\text{number}}\text{,}\) which makes the loop much faster for large inputs. The break command exits as soon as a divisor is found.

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