I think what you're missing is what you actually typed in the first case.

This is a type error, it will not compile or run:

chopEnds = init $ tail

The $ operator can always be rewritten as parentheses, in this case:

chopEnds = init (tail)

Which has the same incorrectly typed meaning as:

chopEnds = init tail

The "result" you pasted looks equivalent to:

chopEnds = init

Perhaps this is what you typed? In this case the argument tail it will shadow the existing binding of the Prelude tail, which would be confusing so with -Wall it would issue a compiler warning:

chopEnds tail = init $ tail

<interactive>:2:10: warning: [-Wname-shadowing]
This binding for ‘tail’ shadows the existing binding
imported from ‘Prelude’ (and originally defined in ‘GHC.List’)

On Mon, Jan 25, 2021 at 10:16 AM Lawrence Bottorff <borgauf@gmail.com> wrote:

I've got this

> init $ tail [1,2,3]
[2]

and this

> chopEnds = init $ tail
> chopEnds [1,2,3]
[1,2]

What happened? Why is it not just init $ tail [1,2,3] ?

This works fine

> chopEnds2 = init . tail
> chopEnds2 [1,2,3]
[2]

What am I missing?

LB
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