[Tutor] a bug I cannot solve myself ;-)

[bob gailer]

On 3/25/2010 5:39 AM, spir ☣ wrote:
> Hello,
>
>
> I'm writing a kind of language simulation. Here, an expression like "a#3.b" maps to a NamedData node, with an attribute terms=[('.','a'),('#',3),('.'''b')].
> (The lang uses '#' instead of "[...]" for item indexing.)
> When this node is "run", the source code maps to a name lookup operation in current scope, passing the terms attr as argument. Below the code with debug prints and the error I get and cannot understand:
>
> ==================
> class Scope(Code):
>      ...
>      @staticmethod
>      def lookup(scope, terms):
>          ''' actual data refered to by name (or context) terms'''
>          data = scope    # actually, initial container
>          for term in terms:
>              (sign,key) = term
>              print data, (sign,ATTR,sign==ATTR,sign is ATTR), key
>              if sign == "ATTR":    # sign == ATTR='.'
>                  print "getAttr"
>                  data = data.getAttr(key)
>              else:                 # sign == ITEM='#'
>                  print "getItem"
>                  data = data.getItem(key) ####### line 82 #######
>          return data
> === output =======
> currentScope ('.', '.', True, True) a
> getItem
> ... traceback ...
>    File "/home/spir/prog/python/claro/scope.py", line 82, in lookup
>      data = data.getItem(key)
> AttributeError: 'Scope' object has no attribute 'getItem'
> ==================
>
> (Scopes actually have no getIem, they're plain symbol (attribute) containers.)
>
> There must be something such obvious I'm too stupid to see it! What do I overlook?

First you assign data = scope
Then you reassign data = data.getAttr(key) OR data = data.getItem(key)
data no longer refers to scope! Hence the error.


>   How can it branch to the "getItem" side of the choice?
>
>
> Denis
> ________________________________
>
> vit esse estrany ☣
>
> spir.wikidot.com
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-- 
Bob Gailer
919-636-4239
Chapel Hill NC