Copyright | (C) 2013-2016 University of Twente |
---|---|
License | BSD2 (see the file LICENSE) |
Maintainer | Christiaan Baaij <christiaan.baaij@gmail.com> |
Safe Haskell | Trustworthy |
Language | Haskell2010 |
Extensions |
|
Documentation
data Index (n :: Nat) Source #
Arbitrary-bounded unsigned integer represented by ceil(log_2(n))
bits.
Given an upper bound n
, an Index
n
number has a range of: [0 .. n
-1]
>>>
maxBound :: Index 8
7>>>
minBound :: Index 8
0>>>
read (show (maxBound :: Index 8)) :: Index 8
7>>>
1 + 2 :: Index 8
3>>>
2 + 6 :: Index 8
*** Exception: X: Clash.Sized.Index: result 8 is out of bounds: [0..7] ...>>>
1 - 3 :: Index 8
*** Exception: X: Clash.Sized.Index: result -2 is out of bounds: [0..7] ...>>>
2 * 3 :: Index 8
6>>>
2 * 4 :: Index 8
*** Exception: X: Clash.Sized.Index: result 8 is out of bounds: [0..7] ...
Index has the type role
>>>
:i Index
type role Index nominal ...
as it is not safe to coerce between different range Index. To change the
size, use the functions in the Resize
class.
Instances
bv2i :: KnownNat n => BitVector n -> Index (2 ^ n) Source #
An alternative implementation of unpack
for the
Index
data type; for when you know the size of the BitVector
and want
to determine the size of the Index
.
That is, the type of unpack
is:
unpack ::BitVector
(CLog
2 n) ->Index
n
And is useful when you know the size of the Index
, and want to get a value
from a BitVector
that is large enough (CLog 2 n
) enough to hold an
Index
. Note that unpack
can fail at run-time when
the value inside the BitVector
is higher than 'n-1'.
bv2i
on the other hand will never fail at run-time, because the
BitVector
argument determines the size.