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# Swift Operators Precedence and Associativity

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This tutorial belongs to the Swift series

Think about this expression:

``````let amount = 1 + 2 * 3
``````

The value of `amount` could drastically change depending if `1 + 2` is calculated before `2 * 3`.

The order of calculation is determined by the operator precedence. From higher precedence to lower precedence, as for the most popular operators we have:

• Multiplication (`*`), division (`/`), remainder (`%`)
• Add (`+`), subtract (`-`)
• Comparisons (`==`, `!=`, `<`, `>`, `<=`, `>=`)
• Logical AND (`&&`) and OR (`||`)
• Ternary conditional (`?:`)
• Assignment and compound assignment operators (`=`, `+=` and so on)

This means that the above expression is resolved first calculating the multiplication, and then the sum:

``````let amount = 1 + 2 * 3 // = 7
``````

The full table of precedence, more complicated, is available at https://developer.apple.com/documentation/swift/swift_standard_library/operator_declarations.

When inside an expression you have multiple operators with the same precedence, we make use of the operator associativity. Associativity is a property we use to determine which operation has priority when the precedence is the same.

For example, consider this:

``````let amount = 4 / 2 * 5
``````

Depending if we first execute `4 / 2` or `2 * 5`, the result could be `10` or `0,4`.

Associativity solves this. Multiplication is left associative, so we must first execute the expression on the left. Parentheses help us figure this out:

``````let amount = (4 / 2) * 5
``````

Multiplication (`*`), division (`/`), remainder (`%`), add (`+`), subtract (`-`), logical AND (`&&`), logical OR (`||`) are left associative

Assignment and compound assignment operators (`=`, `+=` and so on) and the ternary conditional (`?:`) are right associative

Comparisons (`==`, `!=`, `<`, `>`, `<=`, `>=`) don’t have associativity.

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