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Compound assignment operators

Swift has shorthand operators that combine one operator with an assignment, so you can change a variable in place. These look like the existing operators you know – +, -, *, and /, but they have an = on the end because they assign the result back to whatever variable you were using.

For example, if someone scored 95 in an exam but needs to be penalized 5 points, you could write this:

var score = 95
score -= 5

Similarly, you can add one string to another using +=:

var quote = "The rain in Spain falls mainly on the "
quote += "Spaniards"
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