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I'm messing around with a Flappy Bird clone, and i can't figure out what the meaning of the following code is
let birdCategory: UInt32 = 1 << 0
let worldCategory: UInt32 = 1 << 1
let pipeCategory: UInt32 = 1 << 2
let scoreCategory: UInt32 = 1 << 3
Sorry if this is obvious, i've tried looking for the answer but couldn't find it. Thanks
843
Shift Left is a practice intended to find and prevent defects early in the software delivery process. The idea is to improve quality by moving tasks to the left as early in the lifecycle as possible. Shift Left testing means testing earlier in the software development process.
The left-shift of 1 by i is equivalent to 2 raised to power i. As mentioned in point 1, it works only if numbers are positive.
Explanation: Left Shift Operator << shifts bits on the left side and fills Zeroes on the Right end.
The expression represented by the expression pattern is compared with the value of an input expression using the Swift standard library ~= operator. The matches succeeds if the ~= operator returns true . By default, the ~= operator compares two values of the same type using the == operator.
That's the bitwise left shift operator
Basically it's doing this
// moves 0 bits to left for 00000001
let birdCategory: UInt32 = 1 << 0
// moves 1 bits to left for 00000001 then you have 00000010
let worldCategory: UInt32 = 1 << 1
// moves 2 bits to left for 00000001 then you have 00000100
let pipeCategory: UInt32 = 1 << 2
// moves 3 bits to left for 00000001 then you have 00001000
let scoreCategory: UInt32 = 1 << 3
You end up having
birdCategory = 1
worldCategory = 2
pipeCategory = 4
scoreCategory= 8
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