diff --git a/aern2-real.cabal b/aern2-real.cabal
--- a/aern2-real.cabal
+++ b/aern2-real.cabal
@@ -5,7 +5,7 @@
 -- see: https://github.com/sol/hpack
 
 name:           aern2-real
-version:        0.2.12.0
+version:        0.2.13.0
 synopsis:       Real numbers as convergent sequences of intervals
 description:    Please see the README on GitHub at <https://github.com/michalkonecny/aern2/#readme>
 category:       Math
diff --git a/changelog.md b/changelog.md
--- a/changelog.md
+++ b/changelog.md
@@ -1,6 +1,8 @@
 # Change log for aern2-real
 
 * current
+* v 0.2.13 2023-04-07
+  * unsafeApproximationExtension
 * v 0.2.12 2023-04-07
   * more instances for if-then-else with CKleenean
   * or_countable and and_countable for CKleenean
diff --git a/src/AERN2/Real.hs b/src/AERN2/Real.hs
--- a/src/AERN2/Real.hs
+++ b/src/AERN2/Real.hs
@@ -12,12 +12,14 @@
 -}
 module AERN2.Real
 (
-   -- * real numbers and conversions
-   CReal, 
+   -- * sequences of approximants
    CSequence (..), 
-   creal, HasCReals, CanBeCReal,
    cseqPrecisions, cseqIndexForPrecision, 
    cseqFromWithCurrentPrec, cseqFromPrecFunction,
+   unsafeApproximationExtension,
+   -- * real numbers and conversions
+   CReal, 
+   creal, HasCReals, CanBeCReal,
    pi,
    crealFromWithCurrentPrec, crealFromPrecFunction,
    -- * limits
@@ -25,6 +27,7 @@
    -- * lazy Kleeneans
    CKleenean, CanBeCKleenean, ckleenean, 
    CanSelect(..), CanSelectBool, CanSelectCNBool,
+   CanAndOrCountable(..),
    -- * extracting approximations
    CanExtractApproximation(..), (?), bits, prec,
    -- * abstract real numbers
diff --git a/src/AERN2/Real/Type.hs b/src/AERN2/Real/Type.hs
--- a/src/AERN2/Real/Type.hs
+++ b/src/AERN2/Real/Type.hs
@@ -83,6 +83,11 @@
   where
   withP p = runWithPrec p withCurrentP :: CN b
 
+unsafeApproximationExtension :: (CSequence b -> t) -> (CN b -> t)
+unsafeApproximationExtension f b = f (CSequence $ repeat b) 
+  -- a sequence that does not converge unless b is exact
+  -- (eg a fake real number given by an interval)
+
 {- Error handling -}
 
 instance CN.CanTakeErrors CN.NumErrors (CSequence t) where