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"meta-programming" ?

  • To: mathgroup at
  • Subject: [mg60908] "meta-programming" ?
  • From: Jack Goldberg <jackgoldberg at>
  • Date: Mon, 3 Oct 2005 04:06:06 -0400 (EDT)
  • Sender: owner-wri-mathgroup at

Hello once again,

I tend to use a lot of Modules in my programming style.  Here is a  
model example:

      myfunction[   ] := Module[ {L1, L2, L3},
         L1 =  some computations;
         L2 =  more computations;
         L3 =  more computations;
                 final touches

When it comes time to check special (extreme) cases I use the simple  
scheme of sequencially commenting out lines to see what has  
happened.  In the next example I comment out lines  L3 to LN  (here  
L3 is the last  labeled line).

      myfunction[ f__  ] := Module[ {L1, L2, L3},
         L1 =  some computations;
         L2 =  more computations (*;
         L3 =  more computations;
                 final touches *)

If the output is what I expect, I comment out  L3, etc.  So, in  
short, if there are 10 lines of code in my module, I start with line  
L1 and proceed to L10.  When every line does as expected, I try the  
function on still another special case.

Now my question.  Can a "meta" program be constructed which does this  
automatically?  Specifically, this metaprogram takes the input is     
myfunction  and a specific input  f  to myfunction. The metaprogram  
returns the output of each line of the module evaluated for the  
specific input   f  to myfunction thus saving me the bother of  
commenting out each line, one at a time for each extreme input to   
myfunction.  (An extreme input might be an empty sum or a sum with  
just one term, to take two easy examples.  Of course, this kind of  
thing happens when myfunction  is deeply embedded in other code.)

Obviously, I am reluctant to use Trace or any of its variations.  But  
perhaps some version of Trace is the way to go.  Well, at the very  
least I can stick to the old fashion way, "one line at a time".


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