ValueQ
- To: mathgroup at smc.vnet.net
- Subject: [mg34327] ValueQ
- From: rainer <rainer.gruber at gmx.at>
- Date: Wed, 15 May 2002 03:35:17 -0400 (EDT)
- Organization: Johannes Kepler Universitaet Linz
- Sender: owner-wri-mathgroup at wolfram.com
Hi,
I#m searching for a simple workaround of the following behaviour.
For the symbol 'a' I've defined
In[1]:=
a[1] = 2;
When I evaluate ValueQ for a defined and for not a defined expression I
get what I expect:
In[3]:=
ValueQ[a[1]]
Out[3]=
True
In[4]:=
ValueQ[a[2]]
Out[4]=
False
But when I evaluate ValueQ e. g. within a Table I always get True:
In[5]:=
Table[ValueQ[a[i]], {i, 1, 2}]
Out[5]=
{True, True}
The 2nd 'True' is because 'a[i]' is not equal to 'a[2]'. A first
solution to get the expected result is
In[6]:=
Table[ToExpression@("ValueQ[a[" <> ToString[i] <> "]]"), {i, 1, 2}]
Out[6]=
{True, False}
Does anybody know something better?
Rainer Gruber
JOHANNES KEPLER UNIVERSITY LINZ
Institute of Experimental Physics
Atomic Physics and Surface Science