Random C/Objective-C questions

I have come across a few lines of coding I do not understand, and would be grateful for clarification:开发者_如何学Python

1. if(!(counter&7))
2. ds->direction = ts->direction;

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1. if counter is a multiple of 8

2. set the direction element of *ds equal to the direction element of *ts

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The first checks if the result of a bitwise-AND on the counter with 7 is not zero, and the latter assigns the value of the direction member of one struct to the direction member of another.

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1) same as

1. if (!(counter & 7))
2. if ((!(counter & 7)) != 0)
3. if ((counter & 7) == 0)
4. if the lower 3 bits of counter are zero (or if counter is a multiple of 8)

2) same as

1. (*ds).direction = (*ts).direction;
2. set direction of ds (must be of a struct type) to direction of ts