| Copyright | (C) 2016 University of Twente 2017 QBayLogic Google Inc. 2017-2019 Myrtle Software Ltd |
|---|---|
| License | BSD2 (see the file LICENSE) |
| Maintainer | Christiaan Baaij <christiaan.baaij@gmail.com> |
| Safe Haskell | Trustworthy |
| Language | Haskell2010 |
Clash.XException
Description
XException: An exception for uninitialized values
>>>show (errorX "undefined" :: Integer, 4 :: Int)"(*** Exception: X: undefined CallStack (from HasCallStack): ...>>>showX (errorX "undefined" :: Integer, 4 :: Int)"(X,4)"
Synopsis
- newtype XException = XException String
- errorX :: HasCallStack => String -> a
- isX :: a -> Either String a
- hasX :: NFData a => a -> Either String a
- maybeIsX :: a -> Maybe a
- maybeHasX :: NFData a => a -> Maybe a
- fromJustX :: HasCallStack => Maybe a -> a
- undefined :: HasCallStack => a
- xToErrorCtx :: String -> a -> a
- xToError :: HasCallStack => a -> a
- class ShowX a where
- showsX :: ShowX a => a -> ShowS
- printX :: ShowX a => a -> IO ()
- showsPrecXWith :: (Int -> a -> ShowS) -> Int -> a -> ShowS
- seqX :: a -> b -> b
- forceX :: NFDataX a => a -> a
- deepseqX :: NFDataX a => a -> b -> b
- rwhnfX :: a -> ()
- defaultSeqX :: NFDataX a => a -> b -> b
- hwSeqX :: a -> b -> b
- class NFDataX a where
- deepErrorX :: HasCallStack => String -> a
- hasUndefined :: a -> Bool
- ensureSpine :: a -> a
- rnfX :: a -> ()
XException: An exception for uninitialized values
newtype XException Source #
An exception representing an "uninitialized" value.
Constructors
| XException String |
Instances
| Show XException Source # | |
Defined in Clash.XException.Internal Methods showsPrec :: Int -> XException -> ShowS # show :: XException -> String # showList :: [XException] -> ShowS # | |
| Exception XException Source # | |
Defined in Clash.XException.Internal Methods toException :: XException -> SomeException # fromException :: SomeException -> Maybe XException # displayException :: XException -> String # | |
errorX :: HasCallStack => String -> a Source #
Like error, but throwing an XException instead of an ErrorCall
The ShowX methods print these error-values as "X"; instead of error'ing
out with an exception.
isX :: a -> Either String a Source #
Evaluate a value to WHNF, returning Left msgXException.
isX 42 = Right 42 isX (XException msg) = Left msg isX (3, XException msg) = Right (3, XException msg) isX (3, _|_) = Right (3, _|_) isX _|_ = _|_
hasX :: NFData a => a -> Either String a Source #
Fully evaluate a value, returning Left msgXException.
If you want to determine if a value contains undefined parts, use
hasUndefined instead.
hasX 42 = Right 42 hasX (XException msg) = Left msg hasX (3, XException msg) = Left msg hasX (3, _|_) = _|_ hasX _|_ = _|_
If a data structure contains multiple XExceptions, the "first" message is
picked according to the implementation of rnf.
maybeIsX :: a -> Maybe a Source #
Evaluate a value to WHNF, returning Nothing if it throws XException.
maybeIsX 42 = Just 42 maybeIsX (XException msg) = Nothing maybeIsX (3, XException msg) = Just (3, XException msg) maybeIsX (3, _|_) = Just (3, _|_) maybeIsX _|_ = _|_
maybeHasX :: NFData a => a -> Maybe a Source #
Fully evaluate a value, returning Nothing if it throws XException.
maybeHasX 42 = Just 42 maybeHasX (XException msg) = Nothing maybeHasX (3, XException msg) = Nothing maybeHasX (3, _|_) = _|_ maybeHasX _|_ = _|_
fromJustX :: HasCallStack => Maybe a -> a Source #
Same as fromJust, but returns a bottom/undefined value that
other Clash constructs are aware of.
undefined :: HasCallStack => a Source #
Call to errorX with default string
xToErrorCtx :: String -> a -> a Source #
Convert XException to ErrorCall
This is useful when tracking the source of XException that gets eaten up by
pack inside of your circuit; since
pack translates XException into undefined bits.
So for example if you have some large function f:
f a b = ... pack a ... pack b ...
Where it is basically an error if either a or b ever throws an XException,
and so you want that to be reported the moment a or b is used, instead of
it being thrown when evaluating the result of f, then do:
{-# LANGUAGE ViewPatterns #-}
f (xToErrorCtx "a is X" -> a) (xToErrorCtx "b is X" -> b) = ...Where we pass an extra string, for context, to know which argument evaluated
to an XException. We can also use BangPatterns to report the potential
XException being thrown by a or b even earlier, i.e. when f is applied:
{-# LANGUAGE ViewPatterns, BangPatterns #-}
f (xToErrorCtx "a is X" -> !a) (xToErrorCtx "b is X" -> !b) = ...NB: Fully synthesizable, so doesn't have to be removed before synthesis
Example
>>>:set -XViewPatterns -XDataKinds>>>import Clash.Sized.BitVector>>>import GHC.Stack>>>:{let h, h' :: Bit -> BitVector 8 -> BitVector 8 h (xToErrorCtx "a is X" -> a) (xToErrorCtx "b is X" -> b) = slice d7 d0 (pack a ++# b) h' a b = slice d7 d0 (pack a ++# b) :}
>>>h' (errorX "QQ") 30000_0011>>>h (errorX "QQ") 3*** Exception: a is X X: QQ CallStack (from HasCallStack): errorX, called at ...
xToError :: HasCallStack => a -> a Source #
Convert XException to ErrorCall
This is useful when tracking the source of XException that gets eaten up by
pack inside of your circuit; since
pack translates XException into undefined bits.
So for example if you have some large function f:
f a b = ... pack a ... pack b ...
Where it is basically an error if either a or b ever throws an XException,
and so you want that to be reported the moment a or b is used, instead of
it being thrown when evaluating the result of f, then do:
{-# LANGUAGE ViewPatterns #-}
f (xToError -> a) (xToError -> b) = ...Unlike xToErrorCtx, where we have an extra String argument to distinguish
one call to xToError to the other, xToError will use the CallStack
mechanism to aid the user in distinguishing different call to xToError.
We can also use BangPatterns to report the potential XException being
thrown by a or b even earlier, i.e. when f is applied:
{-# LANGUAGE ViewPatterns, BangPatterns #-}
f (xToError -> !a) (xToError -> !b) = ...NB: Fully synthesizable, so doesn't have to be removed before synthesis
Example
>>>:set -XViewPatterns -XDataKinds>>>import Clash.Sized.BitVector>>>import GHC.Stack>>>:{let f, g, h, h' :: HasCallStack => Bit -> BitVector 8 -> BitVector 8 f = g g = h h (xToError -> a) (xToError -> b) = slice d7 d0 (pack a ++# b) h' a b = slice d7 d0 (pack a ++# b) :}
>>>h' (errorX "QQ") 30000_0011>>>f (errorX "QQ") 3*** Exception: CallStack (from HasCallStack): xToError, called at ... h, called at ... g, called at ... f, called at ... X: QQ CallStack (from HasCallStack): errorX, called at ...
Printing XExceptions as "X"
Like the Show class, but values that normally throw an XException are
converted to "X", instead of error'ing out with an exception.
>>>show (errorX "undefined" :: Integer, 4 :: Int)"(*** Exception: X: undefined CallStack (from HasCallStack): ...>>>showX (errorX "undefined" :: Integer, 4 :: Int)"(X,4)"
Can be derived using Generics:
{-# LANGUAGE DeriveGeneric, DeriveAnyClass #-}
import Clash.Prelude
import GHC.Generics
data T = MkTA Int | MkTB Bool
deriving (Show,Generic,ShowX)Minimal complete definition
Nothing
Methods
showsPrecX :: Int -> a -> ShowS Source #
Like showsPrec, but values that normally throw an XException are
converted to "X", instead of error'ing out with an exception.
Like show, but values that normally throw an XException are
converted to "X", instead of error'ing out with an exception.
showListX :: [a] -> ShowS Source #
Like showList, but values that normally throw an XException are
converted to "X", instead of error'ing out with an exception.
Instances
showsX :: ShowX a => a -> ShowS Source #
Like shows, but values that normally throw an XException are
converted to "X", instead of error'ing out with an exception.
printX :: ShowX a => a -> IO () Source #
Like print, but values that normally throw an XException are
converted to "X", instead of error'ing out with an exception
showsPrecXWith :: (Int -> a -> ShowS) -> Int -> a -> ShowS Source #
Use when you want to create a ShowX instance where:
- There is no
Genericinstance for your data type - The
Genericderived ShowX method would traverse into the (hidden) implementation details of your data type, and you just want to show the entire value as "X".
Can be used like:
data T = ... instance Show T where ... instance ShowX T where showsPrecX = showsPrecXWith showsPrec
Strict evaluation
forceX :: NFDataX a => a -> a Source #
a variant of deepseqX that is useful in some circumstances:
forceX x = x `deepseqX` x
deepseqX :: NFDataX a => a -> b -> b infixr 0 Source #
deepseqX: fully evaluates the first argument, before returning the
second. Does not propagate XExceptions.
defaultSeqX :: NFDataX a => a -> b -> b infixr 0 Source #
hwSeqX :: a -> b -> b infixr 0 Source #
Like seqX in simulation, but will force its first argument to be rendered
in HDL. This is useful for components that need to be rendered in hardware,
but otherwise have no meaning in simulation. An example of such a component
would be an ILA: a component monitoring an internal signal of a design. The
output of such a component (typically a unit) can be passed as the first
argument to hwSeqX to ensure the ILA ends up in the generated HDL.
NB: the result of hwSeqX must (indirectly) be used at the very top of
a design. If it's not, Clash will remove it like it does for any other unused
circuit parts.
NB: Make sure the blackbox for the component with zero-width results
uses RenderVoid
Structured undefined / deep evaluation with undefined values
class NFDataX a where Source #
Class that houses functions dealing with undefined values in Clash. See
deepErrorX and rnfX.
Minimal complete definition
Nothing
Methods
deepErrorX :: HasCallStack => String -> a Source #
Create a value where all the elements have an errorX,
but the spine is defined.
default deepErrorX :: (HasCallStack, Generic a, GDeepErrorX (Rep a)) => String -> a Source #
hasUndefined :: a -> Bool Source #
Determines whether any of parts of a given construct contain undefined parts. Note that a negative answer does not mean its bit representation is fully defined. For example:
>>>m = Nothing :: Maybe Bool>>>hasUndefined mFalse>>>pack m0.>>>hasUndefined (pack m)True
default hasUndefined :: (Generic a, GHasUndefined (Rep a)) => a -> Bool Source #
ensureSpine :: a -> a Source #
Create a value where at the very least the spine is defined. For example:
>>>spined = ensureSpine (errorX "?" :: (Int, Int))>>>case spined of (_, _) -> 'a''a'>>>fmap (const 'b') (ensureSpine undefined :: Vec 3 Int)<'b','b','b'>>>>fmap (const 'c') (ensureSpine undefined :: RTree 2 Int)<<'c','c'>,<'c','c'>>
For users familiar with lazyV: this is the generalized
version of it.
default ensureSpine :: (Generic a, GEnsureSpine (Rep a)) => a -> a Source #
Evaluate a value to NF. As opposed to NFDatas
rnf, it does not bubble up XExceptions.