diff options
| author | Herbert Valerio Riedel <hvr@gnu.org> | 2014-11-22 14:52:04 +0100 |
|---|---|---|
| committer | Herbert Valerio Riedel <hvr@gnu.org> | 2014-11-22 15:14:02 +0100 |
| commit | 4b6537677fa9460ca5febe2eb79a2d9d5bdadba2 (patch) | |
| tree | 5f4bde961790a80c0fd915b87ced8816fed82fde /libraries/base/GHC/Natural.hs | |
| parent | 5ea3ee02c7e616235508f1829f8ccfd6047eaf98 (diff) | |
| download | haskell-4b6537677fa9460ca5febe2eb79a2d9d5bdadba2.tar.gz | |
Add `isValidNatural` predicate (#9818)
This predicate function encodes the internal `Natural` invariants, and
is useful for testsuites or code that directly constructs `Natural`
values.
C.f. `integer-gmp2`'s `isValidBigNat#` and `isValidInteger#` predicates
for testing internal invariants.
Diffstat (limited to 'libraries/base/GHC/Natural.hs')
| -rw-r--r-- | libraries/base/GHC/Natural.hs | 21 |
1 files changed, 21 insertions, 0 deletions
diff --git a/libraries/base/GHC/Natural.hs b/libraries/base/GHC/Natural.hs index 7c362ace56..0dead29e64 100644 --- a/libraries/base/GHC/Natural.hs +++ b/libraries/base/GHC/Natural.hs @@ -35,6 +35,7 @@ module GHC.Natural -- (i.e. which constructors are available) depends on the -- 'Integer' backend used! Natural(..) + , isValidNatural -- * Conversions , wordToNatural , naturalToWordMaybe @@ -87,6 +88,17 @@ data Natural = NatS# GmpLimb# -- ^ in @[0, maxBound::Word]@ deriving (Eq,Ord) -- NB: Order of constructors *must* -- coincide with 'Ord' relation +-- | Test whether all internal invariants are satisfied by 'Natural' value +-- +-- This operation is mostly useful for test-suites and/or code which +-- constructs 'Integer' values directly. +-- +-- /Since: 4.8.0.0/ +isValidNatural :: Natural -> Bool +isValidNatural (NatS# _) = True +isValidNatural (NatJ# bn) = isTrue# (isValidBigNat# bn) + && I# (sizeofBigNat# bn) > 0 + {-# RULES "fromIntegral/Natural->Natural" fromIntegral = id :: Natural -> Natural "fromIntegral/Natural->Integer" fromIntegral = toInteger :: Natural->Integer @@ -397,6 +409,15 @@ naturalToInt (NatJ# bn) = I# (bigNatToInt bn) newtype Natural = Natural Integer -- ^ __Invariant__: non-negative 'Integer' deriving (Eq,Ord,Ix) +-- | Test whether all internal invariants are satisfied by 'Natural' value +-- +-- This operation is mostly useful for test-suites and/or code which +-- constructs 'Integer' values directly. +-- +-- /Since: 4.8.0.0/ +isValidNatural :: Natural -> Bool +isValidNatural (Natural i) = i >= 0 + instance Read Natural where readsPrec d = map (\(n, s) -> (Natural n, s)) . filter ((>= 0) . (\(x,_)->x)) . readsPrec d |