[clean-list] Troubles using a function as parameter to another function

[Diederik van Arkel]

op 2/14/02 8:03 PM schreef Claudio Potenza op claudio.potenza@mclink.it:

> After the "more than one Start rule confuses the IDE" problem (that
> was really a bug in the IDE) here is another one:
> 

Sorry about that :-(

> 
> Unfortunately this involve showing a bit of code; I have tried to reduce
> it to the minimum possible; look at the function "processFiles" in the
> following:

[snip code]

> I get this error:
> 
> Uniqueness error [test.icl,5,Start]:"argument 1 of processFiles"
> attribute at  indicated position could not be coerced
> (File -> (*File -> ^ *(*Files -> *(String,*File,*Files))))
> 
> I have found a workaround for this by playing around with the definition of
> the function "doWork", but it is so ugly I don't want to show it here!
> Another strange fact is that if I defined a function "doWork" that doesn't
> have the "*Files" parameter, but only the two File, it works!
> 
> I cannot understand why this happen (and the exact meaning of the error
> message). Am I overlooking something about the uniqueness typing?
> 
> thanks
> 
> 
> Claudio Potenza
> claudio.potenza@mclink.it
> 

I'm sure someone else can explain the error you get better than I can. The
easiest solution here is to tuple the function arguments. The following
version compiles without errors:

Start :: *World -> String
Start world = processFiles doWork "input.txt" "out.txt" world

processFiles :: !((File, *File, *Files) -> (String,*File,*Files)) String
String *World -> String
processFiles doWork inputName outputName world = undef

doWork :: (File, *File, *Files) -> (String,*File,*Files)
doWork (inF, outF, files) = undef

Regards,

Diederik van Arkel