add minimum/maximum

src/Data/Vec.hs

@@ -22,7 +22,7 @@ import Data.Nat
 import Data.Bool
 import Data.Char         (Char)
 import Data.Function     ((∘), ($))
-import Data.TypeClass    (Show, IsList, IsString, Eq, Num)
+import Data.TypeClass    (Show, Eq, Ord, Num, IsList, IsString)
 import Data.Singletons   (SingI, sing)
 
 import qualified Data.TypeClass as T
@@ -203,10 +203,11 @@ foldl₁ (⊗) (x :- y :- ys) = foldl₁ (⊗) (x ⊗ y :- ys)
 
 -- | As for 'foldl', a variant of 'foldr' with no starting point
 foldr₁ ∷ (a → a → a) → Vec a (S n) → a
-foldr₁ (⊗) (x :- Nil)     = x
+foldr₁ _   (x :- Nil)     = x
 foldr₁ (⊗) (x :- y :- ys) = x ⊗ (foldr₁ (⊗) (y :- ys))
 
 
+
 -- * Special folds
 
 -- | The concatenation of all the elements of a vector of vectors.
@@ -259,6 +260,16 @@ all _ Nil       = T
 all p (x :- xs) = and (map p (x :- xs))
 
 
+-- | The least element of a vector.
+minimum ∷ Ord a ⇒ Vec a (S n) → a
+minimum = foldr₁ T.min
+
+
+-- | The largest element of a vector.
+maximum ∷ Ord a ⇒ Vec a (S n) → a
+maximum = foldr₁ T.max
+
+
 -- | The 'sum' function computes the sum of the numbers of a vector.
 sum ∷ Num a ⇒ Vec a n → a
 sum = foldr (T.+) 0
@@ -283,6 +294,7 @@ drop SZ     x         = x
 drop (SS n) (x :- xs) = drop n xs
 
 
+
 -- * Zipping and unzipping vectors
 
 -- | 'zip' takes two vectors and returns a vector of corresponding pairs.
@@ -310,8 +322,8 @@ zipWith _ _ Nil = Nil
 zipWith (⊗) (x :- xs) (y :- ys) = x ⊗ y :- zipWith (⊗) xs ys
 
 
--- | 'unzip' transforms a list of pairs into a list of first components
--- and a list of second components.
+-- | 'unzip' transforms a vectors of pairs into a vector of first components
+-- and a vector of second components.
 unzip ∷ Vec (a, b) n → (Vec a n, Vec b n)
 unzip Nil             = (Nil, Nil)
 unzip ((x, y) :- xys) = (x :- xs, y :- ys)