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Logical Operators
Controlling Order of Execution

Instead of relying on the compiler to set operator precedence, we can do so ourselves by wrapping a logical expression in parentheses, (). The use of parentheses also makes our code easier to read and interpret.

Assume the following logical expression with multiple logical operators:

true || true && false && true

The order of execution may seem unclear at first but following Swift’s operator precedence rules, we achieve the Boolean outcome, true:

Diagram showing flow of operations of a logical expression without parentheses

If we wanted more control of the evaluation of this expression, we can use parentheses to direct order of execution and improve the expression’s readability:

(true || true) && (false && true)
Diagram showing flow of operations of a logical expression with parentheses

Notice how although the expressions utilize the same operators, their outcomes are different. The presence of parentheses overrides Swift’s operator precedence rules and dictates order of operations.

Instructions

1.

In Practice.swift, we’ve set up multiple expressions that are missing certain logical operators.

Add a logical operator, && or ||, in place of ___ to complete the logical expressions.

  • bool1 and bool2 should be true.
  • bool3 should be false.

Note: You will see an error in the terminal on the right if there are still any ___ present in your code. The error should go away after you’ve replaced each ___ with an operator.

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