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Why Evaluate[Defer[1+1]] does not return 2 ?
*To*: mathgroup at smc.vnet.net
*Subject*: [mg110938] Why Evaluate[Defer[1+1]] does not return 2 ?
*From*: "Nasser M. Abbasi" <nma at 12000.org>
*Date*: Mon, 12 Jul 2010 07:22:11 -0400 (EDT)
*Reply-to*: nma at 12000.org
I am a little confused about Defer:
r = Defer[1 + 1]
Out[106]= 1 + 1
Evaluate[r]
Out[109]= 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[117]:= r
Out[117]= 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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