| Re: bug? or how to distinguish between a Hash and an array of Hashes ? [message #83389] |
Mon, 04 March 2013 08:37  |
markb77
Messages: 217
Registered: July 2006
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Senior Member |
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thanks. Even for someone familiar with IDL, this seems somewhat
backwards. For the rest of the IDL data types we can distinguish
between array and scalar objects using SIZE(x, /N_Dimensions)... no?
Now for lists and hashes we have to check the typename() for HASH vs
OBJREF ? that can't be how it was intended..?
-Mark
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| Re: bug? or how to distinguish between a Hash and an array of Hashes ? [message #83390 is a reply to message #83389] |
Mon, 04 March 2013 08:28  |
wlandsman
Messages: 743
Registered: June 2000
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Senior Member |
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The documentation for TYPENAME() explains that it is not exactly the same as SIZE(/TNAME)
"If Variable is a scalar object or a one-element object array, Result will be the object class name. If Variable is an object array with two or more elements, Result will be the IDL basic type name “OBJECT” [because each element of the object array could have a different class name]."
So with a scalar hash, TYPENAME() can return "HASH" but for an array it will return OBJREF (not "OBJECT" as the documentation wrongly says). --Wayne
On Monday, March 4, 2013 11:24:49 AM UTC-5, David Fanning wrote:
> David Fanning writes:
>
>
>
>>
>
>> wlandsman writes:
>
>>
>
>>> You could use the TYPENAME function to distinguish the two variables
>
>>>
>
>>> IDL> print,typename(a)
>
>>> HASH
>
>>> IDL> print,typename(c)
>
>>> OBJREF
>
>>>
>
>>> although I'm not sure why SIZE(/TNAME) doesn't give the same results.
>
>>
>
>> Oh, dear! Really!?
>
>
>
> I guess this is right, though, since there are no "type" codes for hash
>
> or list. They are objects, I guess, not real data types.
>
>
>
> Still, awfully confusing to explain to a new user not familiar with the
>
> "IDL Way". ;-)
>
>
>
> Cheers,
>
>
>
> David
>
>
>
>
>
> --
>
> David Fanning, Ph.D.
>
> Fanning Software Consulting, Inc.
>
> Coyote's Guide to IDL Programming: http://www.idlcoyote.com/
>
> Sepore ma de ni thue. ("Perhaps thou speakest truth.")
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| Re: bug? or how to distinguish between a Hash and an array of Hashes ? [message #83391 is a reply to message #83390] |
Mon, 04 March 2013 08:24 |
David Fanning
Messages: 11724
Registered: August 2001
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Senior Member |
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David Fanning writes:
>
> wlandsman writes:
>
>> You could use the TYPENAME function to distinguish the two variables
>>
>> IDL> print,typename(a)
>> HASH
>> IDL> print,typename(c)
>> OBJREF
>>
>> although I'm not sure why SIZE(/TNAME) doesn't give the same results.
>
> Oh, dear! Really!?
I guess this is right, though, since there are no "type" codes for hash
or list. They are objects, I guess, not real data types.
Still, awfully confusing to explain to a new user not familiar with the
"IDL Way". ;-)
Cheers,
David
--
David Fanning, Ph.D.
Fanning Software Consulting, Inc.
Coyote's Guide to IDL Programming: http://www.idlcoyote.com/
Sepore ma de ni thue. ("Perhaps thou speakest truth.")
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| Re: bug? or how to distinguish between a Hash and an array of Hashes ? [message #83393 is a reply to message #83392] |
Mon, 04 March 2013 08:11 |
wlandsman
Messages: 743
Registered: June 2000
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Senior Member |
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You could use the TYPENAME function to distinguish the two variables
IDL> print,typename(a)
HASH
IDL> print,typename(c)
OBJREF
although I'm not sure why SIZE(/TNAME) doesn't give the same results. --Wayne
On Monday, March 4, 2013 11:05:03 AM UTC-5, superchromix wrote:
> surprisingly, the ISA function doesn't help here either...
>
>
>
>
>
> pro test
>
>
>
> a = hash('first', 1, 'second', 2)
>
> b = hash('third', 3, 'fourth', 4, 'fifth', 5)
>
>
>
> print, 'Output of SIZE() for a HASH varible:'
>
> print, size(a, /STRUCTURE)
>
>
>
> c = [a,b]
>
> print, 'Output of SIZE() for an array of HASHes:'
>
> print, size(c, /STRUCTURE)
>
>
>
> print, 'Output of ISA(/ARRAY) for scalar hash:'
>
> print, isa(a, /array)
>
>
>
> print, 'Output of ISA(/ARRAY) for array of hashes:'
>
> print, isa(c, /array)
>
>
>
> help, a, output=ahelp
>
> help, c, output=chelp
>
>
>
> print, 'Help for scalar hash:'
>
> print, ahelp
>
>
>
> print, 'Help for array of hashes:'
>
> print, chelp
>
>
>
> end
>
>
>
> Output of SIZE() for a HASH varible:
>
> { OBJREF 11 0 0 2
>
> 1 2 0 0 0
>
> 0 0 0 0
>
> }
>
> Output of SIZE() for an array of HASHes:
>
> { OBJREF 11 0 0 2
>
> 1 2 0 0 0
>
> 0 0 0 0
>
> }
>
> Output of ISA(/ARRAY) for scalar hash:
>
> 1
>
> Output of ISA(/ARRAY) for array of hashes:
>
> 1
>
> Help for scalar hash:
>
> A HASH <ID=154 NELEMENTS=2>
>
> Help for array of hashes:
>
> C OBJREF = Array[2]
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| Re: bug? or how to distinguish between a Hash and an array of Hashes ? [message #83394 is a reply to message #83393] |
Mon, 04 March 2013 08:05 |
markb77
Messages: 217
Registered: July 2006
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Senior Member |
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surprisingly, the ISA function doesn't help here either...
pro test
a = hash('first', 1, 'second', 2)
b = hash('third', 3, 'fourth', 4, 'fifth', 5)
print, 'Output of SIZE() for a HASH varible:'
print, size(a, /STRUCTURE)
c = [a,b]
print, 'Output of SIZE() for an array of HASHes:'
print, size(c, /STRUCTURE)
print, 'Output of ISA(/ARRAY) for scalar hash:'
print, isa(a, /array)
print, 'Output of ISA(/ARRAY) for array of hashes:'
print, isa(c, /array)
help, a, output=ahelp
help, c, output=chelp
print, 'Help for scalar hash:'
print, ahelp
print, 'Help for array of hashes:'
print, chelp
end
Output of SIZE() for a HASH varible:
{ OBJREF 11 0 0 2
1 2 0 0 0
0 0 0 0
}
Output of SIZE() for an array of HASHes:
{ OBJREF 11 0 0 2
1 2 0 0 0
0 0 0 0
}
Output of ISA(/ARRAY) for scalar hash:
1
Output of ISA(/ARRAY) for array of hashes:
1
Help for scalar hash:
A HASH <ID=154 NELEMENTS=2>
Help for array of hashes:
C OBJREF = Array[2]
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| Re: bug? or how to distinguish between a Hash and an array of Hashes ? [message #83395 is a reply to message #83394] |
Mon, 04 March 2013 06:39 |
markb77
Messages: 217
Registered: July 2006
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Senior Member |
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I've updated this a bit. It seems that the HELP command can
distinguish between the two cases, but SIZE(), even with the /
STRUCTURE keyword specified, cannot.
pro test
a = hash('first', 1, 'second', 2)
b = hash('third', 3, 'fourth', 4, 'fifth', 5)
print, 'Output of SIZE() for a HASH varible:'
print, size(a, /STRUCTURE)
c = [a,b]
print, 'Output of SIZE() for an array of HASHes:'
print, size(c, /STRUCTURE)
help, a, output=ahelp
help, c, output=chelp
print, ahelp
print, chelp
end
IDL> test
Output of SIZE() for a HASH varible:
{ OBJREF 11 0 0 2
1 2 0 0 0
0 0 0 0
}
Output of SIZE() for an array of HASHes:
{ OBJREF 11 0 0 2
1 2 0 0 0
0 0 0 0
}
A HASH <ID=18 NELEMENTS=2>
C OBJREF = Array[2]
so I could solve this by parsing the output of HELP, but this is
strongly discouraged in the documentation for the IDL Help command
itself, as the text formatting of the output from this command my
change...
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| Re: bug? or how to distinguish between a Hash and an array of Hashes ? [message #83470 is a reply to message #83389] |
Mon, 04 March 2013 08:55 |
Lajos Foldy
Messages: 176
Registered: December 2011
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Senior Member |
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On Monday, March 4, 2013 5:37:26 PM UTC+1, superchromix wrote:
> thanks. Even for someone familiar with IDL, this seems somewhat
>
> backwards. For the rest of the IDL data types we can distinguish
>
> between array and scalar objects using SIZE(x, /N_Dimensions)... no?
>
> Now for lists and hashes we have to check the typename() for HASH vs
>
> OBJREF ? that can't be how it was intended..?
>
>
>
> -Mark
Except structures. There is no scalar structure, s={i:0} and a=replicate(s,2) are both arrays.
regards,
Lajos
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| Re: bug? or how to distinguish between a Hash and an array of Hashes ? [message #83471 is a reply to message #83389] |
Mon, 04 March 2013 08:47 |
wlandsman
Messages: 743
Registered: June 2000
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Senior Member |
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I agree. I hope someone from Exelis will eventually chime in as to the best way to distinguish between scalar and array hashes or lists. --Wayne
On Monday, March 4, 2013 11:37:26 AM UTC-5, superchromix wrote:
> thanks. Even for someone familiar with IDL, this seems somewhat
>
> backwards. For the rest of the IDL data types we can distinguish
>
> between array and scalar objects using SIZE(x, /N_Dimensions)... no?
>
> Now for lists and hashes we have to check the typename() for HASH vs
>
> OBJREF ? that can't be how it was intended..?
>
>
>
> -Mark
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| Re: bug? or how to distinguish between a Hash and an array of Hashes ? [message #83472 is a reply to message #83389] |
Mon, 04 March 2013 08:44 |
markb77
Messages: 217
Registered: July 2006
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Senior Member |
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oops I meant "array and scalar variables" above...
to make one other point, the ISA(/ARRAY) function is unambiguous in
its meaning.. it should return true for arrays and false for scalars,
regardless of whether the scalar is an object reference.
unless.. of course, the object refererence refers to an array-like
object I suppose... but in the case of hash objects if you try to do
this:
a=hash('first',1)
and then try to index it with a[0], this throws an error.
confusion! :)
Mark
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