$x >= $x_min and $x <= $x_max and $y >= $y_min and $y <= $y_max
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($x >= $x_min and $x <= $x_max) and ($y >= $y_min and $y <= $y_max)
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The issue with the extra brackets here is to add a structure to the code that simplifies understanding. Instead of having to understand 4 independent logical tests, I have to understand 2 logical tests, then combine them. And once I've worked out the first test is "$x is between $x_min and $x_max", the second test is much easier to work out.

An alternative way to produce the division is simply by using a line break:

$x >= $x_min and $x <= $x_max and
$y >= $y_min and $y <= $y_max
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In any case, a much nicer way to write an interval test (if you're worried about readability) is to put $x on the inside, and keep all comparisons using the same direction:

$x_min <= $x and $x <= $x_max and
$y_min <= $y and $y <= $y_max
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