[Haskell-cafe] Show function a -> String

Ketil Malde ketil at malde.org
Fri Nov 27 10:36:14 EST 2009

Tsunkiet Man <temp.tsun at gmail.com> writes:


someFunction :: Integer -> String
someFunction = show

> However it asks me how my function can fail? Well I know my function fails
> by definition when I do not insert an Integer into SomeFunction. Like
> SomeFunction 2.3425221 

The compiler guarantees that this will not happen, thus your function
will not get the opportunity to fail.

> and now I also know that when I insert a number that
> is very close to zero (I think a denormalized value means that a value is
> very close to zero:

The numbers closest to zero that you are able to pass, are 1 and -1.
Both of which should work, no?

> Now I also know that when I use 'undefined' I would get an error. 

I'd argue that it's not your function that fails, but the parameter
(whose evaluation causes an exception).

> So what other cases are there? 

Well, it might fail to terminate (loop forever).  Semantically, I think
this is treated as _|_ just like passing it 'undefined'.  I think you'll
have a hard time doing this with 'show', though.

> (I asked my question about Floating
> because I guessed it would be similiar to Integers)

Floating point (IEEE 754) has its own set of problems, but in general, I
think 'show' is fairly robust.  But perhaps you can you think of a
resource it can run out of?

If I haven't seen further, it is by standing in the footprints of giants

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