Difference between substitution and evaluation

Hello,

I'm trying to understand evaluation better, in hopes
of improving the Maxima texi documentation.

Evaluation has sometimes (on this mailing list) been
compared to substitution. Substitution I think I understand.

Naively one might assume that evaluation is just a kind
of substitution: instead of explicitly specifying a 
replacement, an atom is replaced by whatever it's bound to.

So, how does this compare to evaluation as it really happens?
If it helps we can restrict consideration to meval
instead of considering ev in all its glory.

Aside from atoms, there are expressions and functions
to worry about. But let's start small.

Fwiw I found all the messages since 2002 which mention both
evaluation and substitution and read them. Maybe there's
something in there which answers these questions, but if
so I didn't comprehend it. 

Thanks for your help,
Robert Dodier


		
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