what does "a & -2" mean? - 未名空间MITBBS历史存档

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what does "a & -2" mean?

what does "a & -2" mean?# Programming - 葵花宝典

s*e2007-09-05 07:09

1 楼

dear people,
if a is an integer, what would "a & -2" mean? It was used to make sure that
the result can be divided by 2, but i dont understand.
thanks.

b*a2007-09-05 07:09

2 楼

a&-2 will clear a's LSB，so a will be even number.

that

【在 s*********e 的大作中提到】

: dear people,
: if a is an integer, what would "a & -2" mean? It was used to make sure that
: the result can be divided by 2, but i dont understand.
: thanks.

s*e2007-09-05 07:09

3 楼

why use "-2"? what is -2?
thanks

【在 b******a 的大作中提到】

: a&-2 will clear a's LSB，so a will be even number.
:
: that

b*a2007-09-05 07:09

4 楼

if you dont know what your machine type, see it is 16bit or 32 bit. you
can not define the second operator. but use -2 you can always get the ri
ght formate as 0xFFFE for 16bit, 0xFFFF FFFE for 32 bit systme

【在 b******a 的大作中提到】

: a&-2 will clear a's LSB，so a will be even number.
:
: that

h*p2007-09-05 07:09

5 楼

是不是～2？

【在 b******a 的大作中提到】

: if you dont know what your machine type, see it is 16bit or 32 bit. you
: can not define the second operator. but use -2 you can always get the ri
: ght formate as 0xFFFE for 16bit, 0xFFFF FFFE for 32 bit systme