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Wolfram Language Symbolic Computations

Get all the symbols with a pattern and save their Own, Down & Up values?

Eric Smith

Eric Smith, Assured Flow Solutions, LLC.

Posted 6 years ago

Example question: I look for all the symbols with a pattern: `foundVars=Names["var"]`. I want to get all their Own, Down, and Up values and save them. I can do this with `Save` but that's not quite my question. I can't do this: `DownValues/@foundVars` Example Question 2: I create a function to check symbol naming: Attributes[checkName]=HoldAll checkName[x_]:=StringMatchQ[SymbolName[x],"var"] But I run into this: in: var3=.; (Clear var3) in: checkName[var3] out: True (so far so good) in: var3 = 2; (give var3 a value) in: checkName[var3] out: SymbolName: Argument 2 at position 1 is expected to be a symbol Looking at the results from `DownValues`, `OwnValues`, etc. I'm guessing the trick has something to do with `HoldPattern`, but I haven't been able to piece it together. Let me know some tricks and best practices when working with symbols.

POSTED BY: Eric Smith

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Anonymous User

Posted 6 years ago

if your trying to preserve them (you said "save them" generically)... you can save the (whole session), a function, or expressions and restore them as .mx i believe. it saves all pertinent info including up/down values. (you don't need to extract info to "save them")

POSTED BY: Anonymous User

Ilian Gachevski

Ilian Gachevski, Wolfram Research

Posted 6 years ago

Try something like In[1]:= var3 = 2; In[2]:= ToExpression[#, InputForm, OwnValues] & /@ Names["var"] Out[2]= {{HoldPattern[var3] :> 2}} In[3]:= Attributes[checkName] = HoldAll; checkName[x_] := StringMatchQ[SymbolName[Unevaluated[x]], "var"] In[5]:= checkName[var3] Out[5]= True

Try something like

In[1]:= var3 = 2;

In[2]:= ToExpression[#, InputForm, OwnValues] & /@ Names["var*"]

Out[2]= {{HoldPattern[var3] :> 2}}

In[3]:= Attributes[checkName] = HoldAll;
        checkName[x_] := StringMatchQ[SymbolName[Unevaluated[x]], "var*"]

In[5]:= checkName[var3]

Out[5]= True

POSTED BY: Ilian Gachevski

Eric Smith

Eric Smith, Assured Flow Solutions, LLC.

Posted 6 years ago

Thank you Illian, that gives me some hints. I've never used the third argument of ToExpression and haven't been able to use Unevaluated effectively. Great suggestions! Appreciate the help!