isevaluated (empty) → 0.1

raw patch · 3 files changed

+42/−0 lines, 3 filesdep +basedep +ghcsetup-changed

Dependencies added: base, ghc

Files

• Data/IsEvaluated.hs +21/−0
• Setup.lhs +3/−0
• isevaluated.cabal +18/−0

@@ -0,0 +1,21 @@+module Data.IsEvaluated(isEvaluated) where++import RtClosureInspect++-- |Checks whether Control.Exception.evaluate (or rwhnf) would do no work+-- when applied to the value. May produce false negatives (where isEvaluated+-- thinks it would, but it actually wouldn't) in some cases.+--+-- Use case: if isEvaluated foo returns True, then evaluate foo will never+-- throw an exception, or indeed take more than constant (small) time.+isEvaluated :: a -> IO Bool+isEvaluated a = (discriminate . tipe) `fmap` getClosureData a+    where+      discriminate Constr          = True+      discriminate Fun             = True+      discriminate (Indirection _) = True+      discriminate (MutVar _)      = True+      discriminate (MVar _)        = True+      discriminate PAP             = True+      -- It might be possible to handle THUNK_SELECTOR specially+      discriminate _               = False

@@ -0,0 +1,3 @@+#!/usr/bin/env runhaskell+> import Distribution.Simple+> main = defaultMain

@@ -0,0 +1,18 @@+name:                isevaluated+version:             0.1+synopsis:            Check whether a value has been evaluated+description:         An IO action to check whether some value has been evaluated.+                     .+                     If isEvaluated returns True, evaluating it to weak-head+                     normal form won't throw exceptions or take time.+category:            Control, Data+license:             PublicDomain+author:              Svein Ove Aas+maintainer:          svein.ove@aas.no+build-type:          Simple+cabal-version:       >= 1.2+stability:           experimental++Library+  build-depends:       base, ghc > 6.10.1, ghc <= 6.10.3+  Exposed-Modules:     Data.IsEvaluated