[Haskell-cafe] The Good, the Bad and the GUI

[Wojtek Narczyński]

On 14.08.2014 16:44, ok at cs.otago.ac.nz wrote:
> It may be familiar, it may be popular, but the answer
> is beyond any reasonable question simply WRONG.

The exactly advantage of a purpose built app over a spreadsheet is that 
it would not let you save the invoice in this state. Indeed, perhaps it 
is a good idea to tell the users that this sum is not their final value. 
For example display a marijuana leaf next to it. Although, I would 
rather use color for that.

> (The emphasis on NEVER is mine.)  I guess now we know one
> more reason why spreadsheet errors are ubiquitous: the
> interface is broken by design.

I like spreadsheets, but they are not an answer to every need.

>
> I have no idea what is customary, but I for d--n sure would not
> use a spreadsheet to do it!  (This being a Haskell mailing list,
> I would investigate the abilities of hLedger.)

Sorry, hledger is a double entry accounting system, it does not issue 
invoices.

>> So in the end you admit that my "design" (scratch, rather) might be what
>> young people might like?
> On the contrary. You are specifying a design that lets invalid data
> enter into computations. I'm saying they would like a design that
> stops invalid data as early as possible.  This is close in spirit
> to the Foo/FooBuilder distinction, where a Foo is never allowed to
> be in an invalid state.
>
>
Pardon me, but are you "young people"?