diff options
Diffstat (limited to 'txr.1')
| -rw-r--r-- | txr.1 | 58 |
1 files changed, 58 insertions, 0 deletions
@@ -38152,6 +38152,63 @@ In other words, the following equivalences hold: (mask a b c ...) <--> (logior (mask a) (mask b) (mask c) ...) .brev +.coNP Function @ bitset +.synb +.mets (bitset << integer ) +.syne +.desc +The +.code bitset +function returns a list of the positions of bits which have a value of +1 in a positive +.meta integer +argument, or the positions of bits which have a value of zero in a negative +.meta integer +argument. The positions are ordered from least to greatest. The least +significant bit has position zero. If +.meta integer +is zero, the empty list +.code nil +is returned. + +A negative integer is treated as an infinite bit two's complement +representation. + +The argument may be a character. + +If +.meta integer +.code x +is non-negative, the following equivalence holds: + +.verb + x <--> [apply mask (bitset x)] +.brev + +That is to say, the value of +.code x +may be reconstituted by applying the bit positions returned by +.code bitset +as arguments to the +.code mask +function. + +The value of a negative +.code x +may be reconstituted from its +.code bitset +as follows: + +.verb + x <--> (pred (- [apply mask (bitset x)])) +.brev + +also, more trivially, thus: + +.verb + x <--> (- [apply mask (bitset (- x))]) +.brev + .coNP Function @ width .synb .mets (width << integer *) @@ -38675,6 +38732,7 @@ which must be an integer. .um width .um logcount +.um bitset .SS* Exception Handling |