[project @ 2005-02-05 00:41:35 by ross]

[ghc-base.git] / GHC / Base.lhs

diff --git a/GHC/Base.lhs b/GHC/Base.lhs
index bf37476..e07e210 100644 (file)
--- a/GHC/Base.lhs
+++ b/GHC/Base.lhs
@@ -672,9 +672,20 @@ id x                       =  x
 lazy :: a -> a
 lazy x = x
 
--- | Assertion function.  This simply ignores its boolean argument.
+-- Assertion function.  This simply ignores its boolean argument.
 -- The compiler may rewrite it to @('assertError' line)@.
 
+-- | If the first argument evaluates to 'True', then the result is the
+-- second argument.  Otherwise an 'AssertionFailed' exception is raised,
+-- containing a 'String' with the source file and line number of the
+-- call to 'assert'.
+--
+-- Assertions can normally be turned on or off with a compiler flag
+-- (for GHC, assertions are normally on unless the @-fignore-asserts@
+-- option is given).  When assertions are turned off, the first
+-- argument to 'assert' is ignored, and the second argument is
+-- returned as the result.
+
 --     SLPJ: in 5.04 etc 'assert' is in GHC.Prim,
 --     but from Template Haskell onwards it's simply
 --     defined here in Base.lhs