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How to evaluate parts of an expression, but not other parts?

• To: mathgroup at smc.vnet.net
• Subject: [mg122659] How to evaluate parts of an expression, but not other parts?
• From: Julian Francis <julian.w.francis at gmail.com>
• Date: Sat, 5 Nov 2011 04:45:28 -0500 (EST)
• Delivered-to: l-mathgroup@mail-archive0.wolfram.com

Dear all,

I'd like to use the TreePlot function to visualise the expression of a
dynamic programming problem I am working on.

If I have something like: ( (a+b) + (c+d )

Mathematica helpfully simplifies this to: a + b + c + d

But I'd prefer it to be in the original form.

I can't write Hold[ ( (a+b) + (c+d) )] because I do want a,b,c & d to
be evaluated.

I want to write something like:
Hold[ ( (Evaluate[a]+Evaluate[b]) + (Evaluate[c]+Evaluate[d]) ) ]

But this just leaves the Evaluate expressions unevaluated.

Any help greatly appreciated.

Thanks,
Julian.

• Follow-Ups:
  • Re: How to evaluate parts of an expression, but not other parts?
    • From: Bob Hanlon <hanlonr357@gmail.com>
  • Re: How to evaluate parts of an expression, but not other parts?
    • From: Andrzej Kozlowski <akoz@mimuw.edu.pl>