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

[Steve Schafer]

On Wed, 13 Aug 2014 22:31:31 +0200, Wojtek Narczy?ski
<wojtek at power.com.pl> wrote:

>Let's say the user entered:
>
>No, Name, Qty, Price
>--------------------------------------------
>1. [        ]   [99] [10]
>2. [Water] [    ] [10]
>3. [Juice]   [  1] [    ]
>
>The GUI should display total of 990

Why? Why are any of these erroneous line items included in the total? I
would argue that an incomplete or otherwise erroneous line item is not
part of the invoice.

I don't know of any (reasonable) online merchant that requires the user
to separately enter item, quantity and price. Typically, the user
interface is designed explicitly to prohibit an incomplete line item of
this sort.

-Steve Schafer