The Fortress Language Specification - CiteSeerX

40.6.10 update(j:IndexInt, v: Bit):
BinaryEndianWordb,bigEndianBytes,bigEndianBits
throws { IndexOutOfBoundsException }
40.6.11 updatenat k(j:IntegerStatick, v: Bit):
BinaryEndianWordb,bigEndianBytes,bigEndianBits
where { k < 2 b }
This is a functional version of subscripted value object assignment: the bit that would be selected from the result by
subscripting it with j is the same as the given bit v , and all other bits are the same as before. Indexing is zero-origin; an
IndexOutOfBoundsException is thrown unless 0 ≤ j < 2 b . If the subscript is a static expression, then its validity
is checked statically, and no exception will occur at run time.
40.6.12 updatenat m(r:RangeOfStaticSizeIndexInt, m, v:BinaryLinearSequence1, m):
BinaryEndianWordb,bigEndianBytes,bigEndianBits
throws { IndexOutOfBoundsException }
40.6.13 updateint a,nat m,int c(r:StaticRangea, m, c, v:BinaryLinearSequence1, m):
BinaryEndianWordb,bigEndianBytes,bigEndianBits
where { 0 ≤ a < 2 b , 0 ≤ a + m · c < 2 b }
This is a functional version of subscripted value object assignment: bits that would be selected from the result by
subscripting it with r are the same as corresponding elements of v , and all other bits are the same as before; specifically,
the bit that would be selected from the result by subscripting it with r.lowerBound + k × r.stride is the same
as element k of v , for all 0 ≤ k < m . Indexing is zero-origin; an IndexOutOfBoundsException is thrown unless
r ⊆ 0 #2 b . If the subscript is a static range, then its validity is checked statically, and no exception will occur at run
time.
40.6.14 lowHalf ():BinaryEndianWordb − 1,bigEndianBytes,bigEndianBits where { b > 0 }
40.6.15 highHalf ():BinaryEndianWordb − 1,bigEndianBytes,bigEndianBits where { b > 0 }
The getters lowHalf and highHalf each return a binary endian word of half the size (in bits) of this binary endian
word, and with the same endian characteristics; lowHalf returns the less significant bits, and highHalf returns the
more significant bits.
∧
property ∀(v) v.lowHalf .bit(m) = v.bit(m)
m←0#2 ∧
b−1
property ∀(v) v.highHalf .bit(m) = v.bit(m + 2 b−1 )
m←0#2 ∧
b−1
property ∀(v) v.lowHalf m = v[if bigEndianBits then m + 2 b−1 else m end]
m←0#2 ∧
b−1
property ∀(v) v.highHalf m = v[if bigEndianBits then m else m + 2 b−1 end]
m←0#2 b−1
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