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

[Wojtek Narczyński]

Dear All,

Haskell is great for great many areas, let me name just two: - parsers, 
translators, interpreters, compilers; highly concurrent systems.

Haskell is however not great for GUIs. I've been thinking a little why 
this is so. I think one of the reasons might be that in Haskell it is 
unusual to deal with data that is incomplete or otherwise erroneous. Let 
me try to explain, what I mean, by example. If you declare Person class 
in Java, you automatically get a thingy that you can readily use in UI 
construction, because all the fields can temporarily be null, even the 
required ones. In Haskell you'd need two data types: the usual proper 
Haskell data type, and another which wraps every field in Maybe, 
facilitates editing, validation, etc. Perhaps it would be possible to 
generate one data type from the other, or generate both from a common 
specification.

Let me write the same thing in other words. It is not controversial to 
say on this list that specifying what is correct means, is a good idea. 
But for GUIs, in addition to the strong type, you need another relaxed 
type to hold the values temporarily, until the human manages to deliver 
correct data, often by trial and error.

Comments welcome.

-- 
Kind regards,
Wojtek Narczyński