Erik de Castro Lopo <mle+hs@mega-nerd.com> wrote:

> Vasili I. Galchin wrote:
>

> >  "where/let" functions use the
> > same name for function parameters as the outer function and hence
> > there is a "shadow" warning from the compiler.
>

> In Haskell there is an easy way around this. Variables can

> be name a, a', a'' and so on. ...
> ... its a good idea to fix these warnings.

I would _strongly_ advise not to do that.  By trying to silence the
spurious warning about shadowing, there is enormous potential to
introduce new bugs that were not there before.

Example:

 f a b = g (a+b) (b-a)
       where g a c = a*c

ghc warns that g's parameter a shadows the parameter to f.  So we
introduce a primed identifier to eliminate the warning:

 f a b = g (a+b) (b-a)
       where g a' c = a*c

Now, no warnings!  But, oops, this function does not do the same thing.
We forgot to add a prime to all occurrences of a on the right-hand-side.