More defined list-to-V/M operators: (|>|), (>|<).

Provides analogs of the (|>) and (><) operators that first apply an
appropriate 'take' to the given lists so that they may be safely used
on lists that are too long (or infinite) -- a feature I find 
particularly useful from the interactive prompt.

As these operators are more defined, I would ask the package maintainer 
to consider, rather than adding (|>|) and (>|<), just updating the
definitions of (|>) and (><) with the new semantics.

1 files changed, 13 insertions, 0 deletions

diff --git a/lib/Data/Packed/Internal/Vector.hs b/lib/Data/Packed/Internal/Vector.hs
index d410c4d..0e6b3f4 100644
--- a/lib/Data/Packed/Internal/Vector.hs
+++ b/lib/Data/Packed/Internal/Vector.hs
@@ -96,6 +96,19 @@ toList v = safeRead v $ peekArray (dim v)
 infixl 9 |>
 n |> l = if length l == n then fromList l else error "|> with wrong size"
 
+{- | Like '(|>)', but explicitly truncates the list, if it is too long.
+
+It may safely be used, for instance, with infinite lists.
+-}
+(|>|) :: (Storable a) => Int -> [a] -> Vector a
+infixl 9 |>|
+n |>| l = if length l' == n then 
+              fromList l' 
+            else 
+              error "|>|: list too short"
+  where l' = take n l
+
+
 -- | access to Vector elements without range checking
 at' :: Storable a => Vector a -> Int -> a
 at' v n = safeRead v $ flip peekElemOff n