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bitwise-utils

Documentation

Additional bitwise routines.

logical-shift-left

[procedure] (logical-shift-left N1 N2) --> integer

Returns left shift of N1 by N2 bits.

N1
integer ; what to shift.
N2
fixnum ; amount to shift.

Aliases arithmetic-shift.

logical-shift-right

[procedure] (logical-shift-right N1 N2) --> integer

Returns right shift of N1 by N2 bits. Sign preserving.

N1
integer ; what to shift.
N2
fixnum ; amount to shift.

arithmetic-shift-left

[procedure] (arithmetic-shift-left N1 N2) --> integer

Returns left shift of N1 by N2 bits.

N1
integer ; what to shift.
N2
fixnum ; amount to shift.

Aliases arithmetic-shift.

arithmetic-shift-right

[procedure] (arithmetic-shift-right N1 N2) --> integer

Returns right shift of N1 by N2 bits. Sign extending.

N1
integer ; what to shift.
N2
fixnum ; amount to shift.

Essentially (arithmetic-shift <> (- <>)).

bitwise-mask

[procedure] (bitwise-mask WID [ON?]) --> integer

Returns WID low-order bits ON?.

WID
fixnum ; mask bit width.
ON?
boolean ; #t is #b1, #f is #b0; default #t.
(bitwise-mask 5 #t) ;=> +0...011111 (#b+011111)
(bitwise-mask 5 #f) ;=> -1...100000 (#b-100000)

bitwise-join

[procedure] (bitwise-join N0 [N1 ...]) --> integer

Returns adjoined bits.

N0
integer ; seed.
N1 ...
integer ... ; adjoins seed left-to-right.
(bitwise-join #b10 #b0000001 #b101) ;=> #b101101

bitwise-split

[procedure] (bitwise-split N WID) --> (list-of integer)

Returns N disjoined every WID bits.

N
integer ; seed.
WID
fixnum ; bit width.
(bitwise-split #xabcdef 4) ;=> (#xa #xb #xc #xd #xe #xf)
(bitwise-split #x-abcdef 4) ;=> (#x-a #x-b #x-c #x-d #x-e #x-f)

bitwise-count

[procedure] (bitwise-count N) --> fixnum

Returns number of set bits in N.

N
integer

bitwise-merge

[procedure] (bitwise-merge MASK N0 N1) --> integer
MASK
integer
N0
integer
N1
integer

Renamed SRFI-60 bitwise-if.

bitwise-nth?

[procedure] (bitwise-nth? INDEX N) --> boolean
INDEX
integer
N
fixnum

Renamed SRFI-60 bit-set?.

bitwise-any?

[procedure] (bitwise-any? N1 N2) --> boolean
N1
integer
N2
integer

Renamed SRFI-60 any-bits-set?.

bitwise-first-set

[procedure] (bitwise-first-set N) --> fixnum
N
integer

Renamed SRFI-60 first-set-bit.

bitwise-reverse

[procedure] (bitwise-reverse N K) --> integer
N
integer
K
fixnum

bitwise-rotate

[procedure] (bitwise-rotate K COUNT LEN) --> integer

Performs (bitwise-field-rotate K COUNT 0 LEN).

K
integer
COUNT
fixnum
LEN
fixnum

bitwise-set-nth

[procedure] (bitwise-set-nth TO INDEX ON?) --> integer
TO
integer
INDEX
fixnum
ON?
boolean ; #t is #b1, #f is #b0

Renamed SRFI-60 (copy-bit k n b); note argument order change.

bitwise-field

[procedure] (bitwise-field N START END) --> integer
N
integer
START
fixnum
END
fixnum

Renamed SRFI-60 bit-field.

bitwise-field-copy

[procedure] (bitwise-field-copy TO FROM START END) --> integer
TO
integer
FROM
integer
START
fixnum
END
fixnum

Renamed SRFI-60 copy-bit-field.

bitwise-field-reverse

[procedure] (bitwise-field-reverse N START END) --> integer
N
integer
START
fixnum
END
fixnum

Renamed SRFI-60 reverse-bit-field.

[procedure] (bitwise-field-rotate N COUNT START END) --> integer
N
integer
COUNT
fixnum
START
fixnum
END
fixnum

Renamed SRFI-60 rotate-bit-field.

integer->list

[procedure] (integer->list K [LEN]) --> (list-of boolean)
K
integer ; integer to represent as a bit list.
LEN
fixnum ; number of bits, default is all bits.

list->integer

[procedure] (list->integer BOOLS) --> integer
BOOLS
list ; treated as (list-of boolean-like)

bitwise-zeros

[procedure] (bitwise-zeros N) --> integer

Return N zero bits.

N
fixnum

bitwise-ones

[procedure] (bitwise-ones N) --> integer

Return N one bits.

N
fixnum

bitwise-abs

[procedure] (bitwise-abs N) --> integer

Should N be negative bitwise-not the result.

N
integer

bitwise-drop-right

[procedure] (bitwise-drop-right N W) --> integer

Drop W left bits of N.

N
integer
W
fixnum

bitwise-cons

[procedure] (bitwise-cons N M) --> integer

Concatenate N & M.

N
integer
M
integer

Usage

 
(import bitwise-utils)

Author

Kon Lovett

Repository

This egg is hosted on the CHICKEN Subversion repository:

https://anonymous@code.call-cc.org/svn/chicken-eggs/release/5/bitwise-utils

If you want to check out the source code repository of this egg and you are not familiar with Subversion, see this page.

Version history
1.3.0
Export useful helpers bitwise-zeros, bitwise-ones, bitwise-abs, bitwise-drop-right, & bitwise-cons.
1.2.2
Fix bitwise->count.
1.2.2
Fix integer->list/list->integer so invertible.
1.2.1
.
1.2.0
Remove srfi-60 module. (Use srfi-60 egg.)
1.1.4
Fix integer->list type.
1.1.3
.
1.1.2
.
1.1.1
.
1.1.0
Add srfi-60 module.
1.0.1
.
1.0.0
Release.

License

This code is in the public domain.