I sent this two months ago but received no response. One of my students asked me this, and I didn't know how to answer, so I asked here. Did it slip in under the radar? Did I ask it in the wrong forum? Or was everyone waiting for someone else to answer? :-)

Todd Wilson

Department of Computer Science

California State University, Fresno

On Sat, Jan 24, 2026 at 1:22 PM Todd Wilson <twilson@csufresno.edu> wrote:

Should maximum and minimum have HasCallStack constraints like head and tail do?

ghci> :type head
head :: GHC.Stack.Types.HasCallStack => [a] -> a
ghci> head []
*** Exception: Prelude.head: empty list
CallStack (from HasCallStack):
error, called at libraries/base/GHC/List.hs:1646:3 in base:GHC.List
errorEmptyList, called at libraries/base/GHC/List.hs:85:11 in base:GHC.List
badHead, called at libraries/base/GHC/List.hs:81:28 in base:GHC.List
head, called at <interactive>:8:1 in interactive:Ghci1
ghci> :type maximum
maximum :: (Foldable t, Ord a) => t a -> a
ghci> maximum []
*** Exception: Prelude.maximum: empty list
CallStack (from HasCallStack):
error, called at libraries/base/GHC/List.hs:1646:3 in base:GHC.List
errorEmptyList, called at libraries/base/GHC/List.hs:717:28 in base:GHC.List
maximum, called at libraries/base/Data/Foldable.hs:745:15 in base:Data.Foldable

Todd Wilson