       Re: Why Evaluate[Defer[1+1]] does not return 2 ?

• To: mathgroup at smc.vnet.net
• Subject: [mg110942] Re: Why Evaluate[Defer[1+1]] does not return 2 ?
• From: "David Park" <djmpark at comcast.net>
• Date: Tue, 13 Jul 2010 05:26:15 -0400 (EDT)

```I think that Defer is intended for something like the following:

{PasteButton[1 + 1], PasteButton[Defer[1 + 1]]}

Evaluate, use the second button, and then evaluate the pasted result.

David Park
djmpark at comcast.net
http://home.comcast.net/~djmpark/

From: Nasser M. Abbasi [mailto:nma at 12000.org]

I am a little confused about Defer:

r = Defer[1 + 1]
Out= 1 + 1

Evaluate[r]
Out= 1 + 1

But help says:

"Defer[expr] returns an object which remains unchanged until it is
explicitly supplied as Mathematica input, and evaluated using
Shift+Enter, Evaluate in Place, etc. "

Isn't typing Evaluate[r]  the same as Evaluate in Place mentioned above?

?Evaluate

"Evaluate[expr]
causes expr to be evaluated even if it appears as the argument of a
function whose attributes specify that it should be held unevaluated."

Isn't "r" above is the object in question whose value is 1+1?

Actually, typing "r" itself, (same as typing Evaluate[r]) does return
"1+1".

In:= r
Out= 1 + 1

I think I know what is the problem now, I am going by that "r" is the
expression whose value is "1+1". I think this is the problem. "r" is not
the expression, it is "1+1" which is the expression. "r" is just another
name for Defer[1+1]. Am i getting close?

--Nasser

```

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