Ulrich,

From what I understand, in your first example, you are saving an expression, your second example, you are saving a procedure.

I recommend using Set and not SetDelayed for the first case. Using your example:

Put[x^2, "test.m"];
g[x_] = Get["test.m"];
g[2]

4

This is not unique to Put/Get. Anytime you need to evaluate an expression and then convert it to a "function", I find using Set (=), to be more clear than trying to deal with Holding, etc.

As to your second example, I would consider using Save[] or DumpSave[] to save your procedure. For example:

In[1]:= ff[z_] := Block[{n}, n = 1; Do[n = n + 1, {z}]; Return[n]]
Save["test.m", ff]
Clear[ff]
Get["test.m"]
ff[3]

Out[5]= 4

The difference is that the Block expression must be delayed so I would use SetDelay here and save it as a function. I hope this helps.

Regards,

Neil

So if you break the code, the rhs for SetDelay is just load the package

every time you call the function g, it just load the file and return x^2. Your second method works because Evaluate around the second argument overwrites the HoldAll attribute of SetDelayed.

In[9]:= Attributes[SetDelayed]
Out[9]= {HoldAll, Protected, SequenceHold}

Great, this works. Meanwhile I also found a solution with packages but this is even simpler. Now, my codes will get much shorter. Thank you very much, Neil.