#
#
# The Nim Compiler
# (c) Copyright 2012 Andreas Rumpf
#
# See the file "copying.txt", included in this
# distribution, for details about the copyright.
#
# this unit handles Nim sets; it implements bit sets
# the code here should be reused in the Nim standard library
type
ElemType = byte
TBitSet* = seq[ElemType] # we use byte here to avoid issues with
# cross-compiling; uint would be more efficient
# however
const
ElemSize* = 8
One = ElemType(1)
Zero = ElemType(0)
template modElemSize(arg: untyped): untyped = arg and 7
template divElemSize(arg: untyped): untyped = arg shr 3
proc bitSetInit*(b: var TBitSet, length: int)
proc bitSetUnion*(x: var TBitSet, y: TBitSet)
proc bitSetDiff*(x: var TBitSet, y: TBitSet)
proc bitSetSymDiff*(x: var TBitSet, y: TBitSet)
proc bitSetIntersect*(x: var TBitSet, y: TBitSet)
proc bitSetIncl*(x: var TBitSet, elem: BiggestInt)
proc bitSetExcl*(x: var TBitSet, elem: BiggestInt)
proc bitSetIn*(x: TBitSet, e: BiggestInt): bool
proc bitSetEquals*(x, y: TBitSet): bool
proc bitSetContains*(x, y: TBitSet): bool
proc bitSetCard*(x: TBitSet): BiggestInt
# implementation
proc bitSetIn(x: TBitSet, e: BiggestInt): bool =
result = (x[int(e.divElemSize)] and (One shl e.modElemSize)) != Zero
proc bitSetIncl(x: var TBitSet, elem: BiggestInt) =
assert(elem >= 0)
x[int(elem.divElemSize)] = x[int(elem.divElemSize)] or
(One shl elem.modElemSize)
proc bitSetExcl(x: var TBitSet, elem: BiggestInt) =
x[int(elem.divElemSize)] = x[int(elem.divElemSize)] and
not(One shl elem.modElemSize)
proc bitSetInit(b: var TBitSet, length: int) =
newSeq(b, length)
proc bitSetUnion(x: var TBitSet, y: TBitSet) =
for i in 0..high(x): x[i] = x[i] or y[i]
proc bitSetDiff(x: var TBitSet, y: TBitSet) =
for i in 0..high(x): x[i] = x[i] and not y[i]
proc bitSetSymDiff(x: var TBitSet, y: TBitSet) =
for i in 0..high(x): x[i] = x[i] xor y[i]
proc bitSetIntersect(x: var TBitSet, y: TBitSet) =
for i in 0..high(x): x[i] = x[i] and y[i]
proc bitSetEquals(x, y: TBitSet): bool =
for i in 0..high(x):
if x[i] != y[i]:
return false
result = true
proc bitSetContains(x, y: TBitSet): bool =
for i in 0..high(x):
if (x[i] and not y[i]) != Zero:
return false
result = true
# Number of set bits for all values of int8
const populationCount: array[uint8, uint8] = block:
var arr: array[uint8, uint8]
proc countSetBits(x: uint8): uint8 =
return
( x and 0b00000001'u8) +
((x and 0b00000010'u8) shr 1) +
((x and 0b00000100'u8) shr 2) +
((x and 0b00001000'u8) shr 3) +
((x and 0b00010000'u8) shr 4) +
((x and 0b00100000'u8) shr 5) +
((x and 0b01000000'u8) shr 6) +
((x and 0b10000000'u8) shr 7)
for it in low(uint8)..high(uint8):
arr[it] = countSetBits(cast[uint8](it))
arr
proc bitSetCard(x: TBitSet): BiggestInt =
for it in x:
result.inc int(populationCount[it])