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)
>
> 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)
>
> 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
>
>
>
> 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 ==============
Forgot to attach my version info
IDL> help, !version
** Structure !VERSION, 8 tags, length=104, data length=100:
ARCH STRING 'x86_64'
OS STRING 'Win32'
OS_FAMILY STRING 'Windows'
OS_NAME STRING 'Microsoft Windows'
RELEASE STRING '8.3'
BUILD_DATE STRING 'Nov 15 2013'
MEMORY_BITS INT 64
FILE_OFFSET_BITS
INT 64
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