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b. Implements Bitwise Operations |
initial writing: 2001-11-22 |
The adverb m b. has been extended to compute
bitwise functions on integer arguments. An argument atom
is treated as a list of length w of bits, where w
is the word size of the underlying machine. m=16+k specifies
the boolean function whose ravelled function table
is #:k .
For example, 17 b. specifies
bitwise and
(17 ↔ 16+1
↔ 16+#.0 0 0 1).
There is special code to effect efficient
execution of the following cases:
| m b."r | monad and dyad | ||
| m b./ | monad and dyad | ||
| m b./\ | monad | ||
| m b./\. | monad |
Finally, 32 b. specifies rotate, 33 b.
specifies shift, and 34 b. specifies signed shift.
See also the
b. entry in the dictionary.
Examples:
12345 (17 b.) 67890 bitwise and
48
f=: (32#2)&#: { '.x'"_
f 12345 67890 48
..................xx......xxx..x
...............x....x..x..xx..x.
..........................xx....
_12345 (23 b.) 67890 bitwise or
_12297
f _12345 67890 _12297
xxxxxxxxxxxxxxxxxx..xxxxxx...xxx
...............x....x..x..xx..x.
xxxxxxxxxxxxxxxxxx..xxxxxxxx.xxx
20 b./~ i.10 bitwise less than table
0 1 2 3 4 5 6 7 8 9
0 0 2 2 4 4 6 6 8 8
0 1 0 1 4 5 4 5 8 9
0 0 0 0 4 4 4 4 8 8
0 1 2 3 0 1 2 3 8 9
0 0 2 2 0 0 2 2 8 8
0 1 0 1 0 1 0 1 8 9
0 0 0 0 0 0 0 0 8 8
0 1 2 3 4 5 6 7 0 1
0 0 2 2 4 4 6 6 0 0
23 b./\ 2^i.10 cumulative bitwise or
1 3 7 15 31 63 127 255 511 1023
_5 (33 b.) 12345 shift
385
f 12345 385
..................xx......xxx..x
.......................xx......x
_5 (33 b.) _12345 shift
134217342
f _12345 134217342
xxxxxxxxxxxxxxxxxx..xxxxxx...xxx
.....xxxxxxxxxxxxxxxxxx..xxxxxx.
_5 (34 b.) _12345 signed shift
_386
f _12345 _386
xxxxxxxxxxxxxxxxxx..xxxxxx...xxx
xxxxxxxxxxxxxxxxxxxxxxx..xxxxxx.