dpb
newbyte bytespec integer ⇒ result-integer
pronounced ,de ’pib or pronounced ,de ’pe b or pronounced ’d\=e ’p\=e ’b\=e
newbyte—an integer.
bytespec—a byte specifier.
integer—an integer.
result-integer—an integer.
dpb (deposit byte) is used to replace a field of bits within integer. dpb returns an integer that is the same as integer except in the bits specified by bytespec.
Let s
be the size specified
by bytespec; then the low s
bits of newbyte appear in
the result in the byte specified by bytespec.
Newbyte is interpreted as
being right-justified, as if it were the result of ldb.
(dpb 1 (byte 1 10) 0) ⇒ 1024 (dpb -2 (byte 2 10) 0) ⇒ 2048 (dpb 1 (byte 2 10) 2048) ⇒ 1024
byte, byte-size, byte-position [Function] , deposit-field [Function] , ldb [Accessor]
(logbitp j (dpb m (byte s p) n)) ≡ (if (and (>= j p) (< j (+ p s))) (logbitp (- j p) m) (logbitp j n))
In general,
(dpb x (byte 0 y) z) ⇒ z
for all valid values of x, y, and z.
Historically, the name “dpb” comes from a DEC PDP-10 assembly language instruction meaning “deposit byte.”