| Copyright | (c) Levent Erkok |
|---|---|
| License | BSD3 |
| Maintainer | erkokl@gmail.com |
| Stability | experimental |
| Safe Haskell | None |
| Language | Haskell2010 |
Data.SBV.Tools.Overflow
Description
Implementation of overflow detection functions. Based on: http://www.microsoft.com/en-us/research/wp-content/uploads/2016/02/z3prefix.pdf
Synopsis
- class ArithOverflow a where
- class (ArithOverflow (SBV a), Num a, SymWord a) => CheckedArithmetic a where
- sFromIntegralO :: forall a b. (Integral a, HasKind a, Num a, SymWord a, HasKind b, Num b, SymWord b) => SBV a -> (SBV b, (SBool, SBool))
- sFromIntegralChecked :: forall a b. (?loc :: CallStack, Integral a, HasKind a, HasKind b, Num a, SymWord a, HasKind b, Num b, SymWord b) => SBV a -> SBV b
Arithmetic overflows
class ArithOverflow a where Source #
Detecting underflow/overflow conditions. For each function, the first result is the condition under which the computation underflows, and the second is the condition under which it overflows.
Methods
bvAddO :: a -> a -> (SBool, SBool) Source #
Bit-vector addition. Unsigned addition can only overflow. Signed addition can underflow and overflow.
A tell tale sign of unsigned addition overflow is when the sum is less than minumum of the arguments.
>>>prove $ \x y -> snd (bvAddO x (y::SWord16)) <=> x + y .< x `smin` yQ.E.D.
bvSubO :: a -> a -> (SBool, SBool) Source #
Bit-vector subtraction. Unsigned subtraction can only underflow. Signed subtraction can underflow and overflow.
bvMulO :: a -> a -> (SBool, SBool) Source #
Bit-vector multiplication. Unsigned multiplication can only overflow. Signed multiplication can underflow and overflow.
bvMulOFast :: a -> a -> (SBool, SBool) Source #
Same as bvMulO, except instead of doing the computation internally, it simply sends it off to z3 as a primitive.
Obviously, only use if you have the z3 backend! Note that z3 provides this operation only when no logic is set,
so make sure to call setLogic Logic_NONE in your program!
bvDivO :: a -> a -> (SBool, SBool) Source #
Bit-vector division. Unsigned division neither underflows nor overflows. Signed division can only overflow. In fact, for each
signed bitvector type, there's precisely one pair that overflows, when x is minBound and y is -1:
>>>allSat $ \x y -> snd (x `bvDivO` (y::SInt8))Solution #1: s0 = -128 :: Int8 s1 = -1 :: Int8 This is the only solution.
bvNegO :: a -> (SBool, SBool) Source #
Bit-vector negation. Unsigned negation neither underflows nor overflows. Signed negation can only overflow, when the argument is
minBound:
>>>prove $ \x -> x .== minBound <=> snd (bvNegO (x::SInt16))Q.E.D.
Instances
| ArithOverflow SVal Source # | |
Defined in Data.SBV.Tools.Overflow | |
| ArithOverflow SInt64 Source # | |
Defined in Data.SBV.Tools.Overflow | |
| ArithOverflow SInt32 Source # | |
Defined in Data.SBV.Tools.Overflow | |
| ArithOverflow SInt16 Source # | |
Defined in Data.SBV.Tools.Overflow | |
| ArithOverflow SInt8 Source # | |
Defined in Data.SBV.Tools.Overflow | |
| ArithOverflow SWord64 Source # | |
Defined in Data.SBV.Tools.Overflow | |
| ArithOverflow SWord32 Source # | |
Defined in Data.SBV.Tools.Overflow | |
| ArithOverflow SWord16 Source # | |
Defined in Data.SBV.Tools.Overflow | |
| ArithOverflow SWord8 Source # | |
Defined in Data.SBV.Tools.Overflow | |
class (ArithOverflow (SBV a), Num a, SymWord a) => CheckedArithmetic a where Source #
A class of checked-arithmetic operations. These follow the usual arithmetic,
except make calls to sAssert to ensure no overflow/underflow can occur.
Use them in conjunction with safe to ensure no overflow can happen.
Methods
(+!) :: (?loc :: CallStack) => SBV a -> SBV a -> SBV a infixl 6 Source #
(-!) :: (?loc :: CallStack) => SBV a -> SBV a -> SBV a infixl 6 Source #
(*!) :: (?loc :: CallStack) => SBV a -> SBV a -> SBV a infixl 7 Source #
(/!) :: (?loc :: CallStack) => SBV a -> SBV a -> SBV a infixl 7 Source #
negateChecked :: (?loc :: CallStack) => SBV a -> SBV a Source #
Instances
Cast overflows
sFromIntegralO :: forall a b. (Integral a, HasKind a, Num a, SymWord a, HasKind b, Num b, SymWord b) => SBV a -> (SBV b, (SBool, SBool)) Source #
Detecting underflow/overflow conditions for casting between bit-vectors. The first output is the result, the second component itself is a pair with the first boolean indicating underflow and the second indicating overflow.
>>>sFromIntegralO (256 :: SInt16) :: (SWord8, (SBool, SBool))(0 :: SWord8,(False,True))>>>sFromIntegralO (-2 :: SInt16) :: (SWord8, (SBool, SBool))(254 :: SWord8,(True,False))>>>sFromIntegralO (2 :: SInt16) :: (SWord8, (SBool, SBool))(2 :: SWord8,(False,False))>>>prove $ \x -> sFromIntegralO (x::SInt32) .== (sFromIntegral x :: SInteger, (false, false))Q.E.D.
As the last example shows, converting to sInteger never underflows or overflows for any value.