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execution model: Function vs. delayed execution

• To: mathgroup at smc.vnet.net
• Subject: [mg121327] execution model: Function vs. delayed execution
• From: Alan <alan.isaac at gmail.com>
• Date: Sat, 10 Sep 2011 07:30:29 -0400 (EDT)
• Delivered-to: l-mathgroup@mail-archive0.wolfram.com
• Reply-to: comp.soft-sys.math.mathematica at googlegroups.com

Warning: I am a Mathematica newbie and not a CS type, so my vocabulary may prove clumsy.

I am used to a deferred execution model of function definition.  Roughly, if I can write code that would be successfully executed outside a function definition, then I can make it a function body by appropriately "wrapping" it.

In Mathematica, I can evaluate the following):
x = {1,1,2}
x=DeleteDuplicates[x]; x
(Note: the redundancy is intentional.)

Next, I attempt to "wrap" this as follows
Clear[x]
Function[x, (x=DeleteDuplicates[x];x)][{1,1,2}]

This produces an error:
Set::shape: "Lists {1,1,2} and {1,2} are not the same shape."

Can you help me understand the execution model that leads to this?

Thanks,
Alan Isaac

• Follow-Ups:
  • Re: execution model: Function vs. delayed execution
    • From: Leonid Shifrin <lshifr@gmail.com>