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Another question about Compile[]:

• To: mathgroup at smc.vnet.net
• Subject: [mg49950] Another question about Compile[]:
• From: gilmar.rodriguez at nwfwmd.state.fl.us (Gilmar Rodr?guez Pierluissi)
• Date: Sat, 7 Aug 2004 03:51:48 -0400 (EDT)
• Sender: owner-wri-mathgroup at wolfram.com

Dear Mathematica Web Group:
I'm attempting to build a Compiled version of the following function:

In[1]:
MGPPP[n_] := Module[{p, q},
    {m = n/2; If[Element[m, 
    Primes], {p = m, q = m}, {k =
       PrimePi[m]; Do[If[Element[n - Prime[i], Primes], hit = i; 
          Break[]], {i, k, 1, -1}], p = Prime[hit], q = n - p}]}; {p, q}]

which works as follows:

In[2]:
MGPPP[400]

Out[2]:
{173, 227}

Unfortunately, my attempt fails:

In[3]:
mgppp = Compile[{{p, _Integer, 
    1}, {q, _Integer, 1}, {n, _Integer, 1}}, Module[{p, q},
      {m = n/2; If[Element[m, Primes], {p = m, q = m}, {
    k = PrimePi[m]; Do[If[Element[n - Prime[i], 
      Primes], hit = i; 
        Break[]], {i, k, 1, -1}], p = Prime[hit], q = n - p}]}; {p, q}]]

Out[3]:
Compile::initvar: The variable p has not been initialized or has been \
initialized to Null.
Compile::cptype: List not supported for type Void; evaluation will use the \
uncompiled function.

Thank you for your help!

• Follow-Ups:
  • Re: Another question about Compile[]:
    • From: DrBob <drbob@bigfoot.com>