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Function DPB

Syntax

  • dpb newbyte bytespec integerresult-integer

Arguments and Values

Description

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.

Examples

(dpb 1 (byte 1 10) 0)

1024

(dpb -2 (byte 2 10) 0)

2048

(dpb 1 (byte 2 10) 2048)

1024

Side Effects

None.

Affected By

None.

Exceptional Situations

None.

See Also

Notes

(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."