Maybe a is a sum type.

Show instance for sum types displays the constructor.

For example, if we used another sum type:

Either Int Int,

then

Left 23 /= Right 23

So we'd be interested to see the constructor to tell them apart. 23 wouldn't be sufficiently clear.

On Wed, May 13, 2020 at 5:18 PM Velichko Lefterov <velichko.lefterov@gmail.com> wrote:

The function returns Maybe a.
On Wed, May 13, 2020 at 5:16 PM Alexander Chen <alexander@chenjia.nl> wrote:
I expected

prelude> safeHead [23,1,4,2,4,2]
23
not
Just 23
May 13, 2020 4:11:47 PM CEST Imants Cekusins <imantc@gmail.com> wrote:
prelude> safeHead [23,1,4,2,4,2]
Just 23

Looks good.

What did you expect to see?
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