On Monday, July 14, 2014 4:24:08 PM UTC+10, SonicKenking wrote:
> Hello Community,
>
>
>
> I tried to implement a special Hash object with following features
>
> 1. Keys are of String type
>
> 2. Keys should be case insensitive
>
> 3. The original cases of keys should be preserved and reported when the keys() method is called.
>
>
>
> Let's say it is called SpeicalHash. It should support following operations:
>
>
>
> h = SpecialHash()
>
> h['X'] = 42
>
> print, h.keys() ; output 'X'
>
> print, h['x'], h['X'] ; output 42, 42
>
> print, h.haskey('x'), h.haskey('X') ; output 1, 1
>
>
>
> h['x'] = 1337
>
> print, h['x'], h['X'] ; output 1337, 1337
>
>
>
> I came up with an implementation (attached at the end of this post) and it meets all of the above requirements. However, when I tried to print the variable h, it reports error of "Key does not exist"
>
>
>
> print, h ; Output % Key does not exist: "X"
>
>
>
> I found out the PRINT command calls Hash::_overloadPrint to do the job and it in turn calls Keys() method to get the keys. I guess that is where the key "X" comes in. However, I don't understand how PRINT gets the value of a key because none of the overload Bracket methods are called (the cases of keys are taken care of in SpecialHash's bracket methods). I can only think of two possibilities:
>
>
>
> 1. The Hash::_overloadPrint method calls Hash's own bracket methods to get the value of a key. Therefore the SpecialHash's bracket methods did not get called. If this is true, it seems to be a bug in IDL's Hash implementation and should be fixed.
>
>
>
> 2. The Hash::_overloadPrint method calls some other hidden method to get the value of a key. If this is the case, can someone show me how it is done?
>
>
>
> Thanks!
>
>
>
> Yang
>
>
>
> ; =============== SpecialHash Implementation Starts Here ==============
>
>
>
>
>
> function SpecialHash::keys
>
> return, list(self.keylist, /extract)
>
> end
>
>
>
> function SpecialHash::hasKey, _keys
>
> keys = strlowcase(_keys)
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> return, self->Hash::hasKey(keys)
>
> end
>
>
>
> function SpecialHash::_overloadBracketsRightSide, isRange, $
>
> sub1, sub2, sub3, sub4, sub5, sub6, sub7, sub8
>
>
>
> sub1 = strlowcase(sub1)
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> return, self->hash::_overloadBracketsRightSide(isRange, sub1, sub2, sub3, sub4, sub5, sub6, sub7, sub8)
>
>
>
> end
>
>
>
> pro SpecialHash::_overloadBracketsLeftSide, objref, value, isrange, $
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> _sub1, sub2, sub3, sub4, sub5, sub6, sub7, sub8
>
>
>
> sub1 = strlowcase(_sub1)
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> self->Hash::_overloadBracketsLeftSide, objref, value, isrange, sub1, sub2, sub3, sub4, sub5, sub6, sub7, sub8
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> if (self->Hash::keys()).count() eq self.keylist.count() + 1 then self.keylist.add, _sub1
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>
>
> end
>
>
>
> function SpecialHash::init
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> if ~self->Hash::init() then return, 0
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> self.keylist = list()
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> return, 1
>
> end
>
>
>
> pro SpecialHash__define
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> class = {SpecialHash, inherits hash, $
>
> keylist: list() }
>
> end
>
>
>
>
>
> ; =============== End of Code ==============
A bit more findings:
This is most likely a bug in 8.3
I tried with 8.2.3 and I didn't get any error with "PRINT, h". As 8.3 added implied print, it is likely where the bug is introduced?
However, one more problem with both 8.2.3 and 8.3 is that the keys shown by PRINT is in wrong case:
IDL> h = SpecialHash()
IDL> h['X'] = 42
IDL> print, h
x: 42
NOTE the x displayed by PRINT is in lowercase while it really should be in uppercase.
The case is also wrong with FOREACH loop
IDL> foreach v,h,k do print, k,v
x 42
Scratching my head ...
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