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

Wojtek Narczyński wojtek at power.com.pl
Thu Aug 14 08:42:41 UTC 2014

On 14.08.2014 03:22, ok at cs.otago.ac.nz 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?  Let's be clear about this: given that
> information, the total is unknown and unknowable,
> and even if lines 1 and 2 were intended to be the
> same line, the existence of line 3 means that 990
> is almost surely LESS than the correct total,
> whatever that might be.

Because this is what you would get in the most familiar software for 
accountants, and the most widespread functional language in the world: a 
spreadsheet. Or simply because this has been specified this way and the 
developer is supposed to implement it.

> Supermarkets here don't let you create invoice lines
> by reference (giving a possibly garbled name) but
> only by ostension ("I want to buy THIS").  This is
> why all those bar codes and thingies exist.
> Libraries here do something similar with books:
> you show the machine "I want to borrow THIS book"
> and a guaranteed valid line is created.

Imagine you are a freelance programmer and you are in the process of 
invoicing your customer.

> A possible data point:  students here are very much
> used to the instant feedback provided by syntax colouring
> editors, and few of them would willingly program without
> such tools.  (I'm annoyed by and slowed by this nonsense, but
> tastes vary.)
Heh, I also like syntax colouring editors, vim specifically. Recently I 
saw SublimeText, and I also liked it very much, I almost switched from 
vim. I keep promising to myself that I would learn Emacs. I don't like 
Eclipse, because it is too slow.

>    This is evidence that at least some people
> strongly prefer instant feedback; by the time they get to
> the end of a form they know that each and every field is
> at least plausible taken by itself.
So in the end you admit that my "design" (scratch, rather) might be what 
young people might like?

Kind regards,
Wojtek Narczynski

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