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Dear Ferreira,<br>
<br>
Any compiler error message that involves the keyword 'uniqueness'
has to do with sharing: in your code, the function doit creates two
references to the value pst:<br>
(1) as second argument of appListPIO<br>
(2) by accessing the ls field of pst (using pst.ls)<br>
This implies that it is not 'unique', i.e.: there exists no longer a
single reference to the value pst. However, the function doit must
produce a value of the same type that has exactly one reference.
This is what the error message says: the demanded (uniqueness)
attribute (which is unique) cannot be offered by shared object (viz.
pst). The trick to get around this is to use argument
pattern-matching on (unique) records. The following should work:<br>
<pre wrap=""> doit [id1,id2] (lst,pst=:{ls})
= (lst+1, appListPIO [(setControlText id1 (toString lst))
,(setControlText id2 ls)
] pst)
</pre>
The difference is that now there is only a single reference to pst
in the result of doit. The reference to ls is now directly 'into'
the pst record, not via the pst record.<br>
<br>
Hope this helps.<br>
<br>
Regards,<br>
Peter<br>
<br>
<br>
On 5/9/2011 5:02 PM, Ferreira Maurizio wrote:
<blockquote
cite="mid:E89B74EF2DA1894882807F197A1212220C69876C5B@itgoa00ms-020.selingdom.local"
type="cite">
<pre wrap="">In the following test, I cannot use pst.ls
I suppose it should be the value used to initialize the process state (e.g. "ps")
The compiler complains about "setControlText id2 pst.ls" (near the end of the program)
whith the error:
Uniqueness error [hello.icl,27,pst]" demanded attribute cannot be offered by shared object
Any suggestion ?
(BTW, is there somewhere an explanation of error messages ?)
Regards.
Maurizio.
module hello
import StdEnv, StdIO
Start world
#(ids,world) = openIds 2 world
= startIO NDI "ps" (snd o openDialog 1 (hello ids) ) [ProcessClose closeProcess] world
where
hello [id1,id2] = Dialog "My dialog"
(TextControl "00" [ControlId id1]
:+:
TextControl "00" [ControlPos (Left, zero), ControlId id2]
:+:
ButtonControl "ok" [ ControlPos (Left, zero)
, ControlViewSize {w=75, h=23}
, ControlFunction (doit [id1,id2])
]
)
[ WindowClose (noLS closeProcess)
, WindowViewSize {w=150, h=90}
, WindowPos (Fix, OffsetVector {vx=400, vy=350})
]
doit [id1,id2] (lst,pst)
= (lst+1, appListPIO [(setControlText id1 (toString lst))
,(setControlText id2 pst.ls)
] pst)
</pre>
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