Hold[], Evaluate[] and so forth.

*To*: mathgroup <mathgroup at yoda.physics.unc.edu>*Subject*: Hold[], Evaluate[] and so forth.*From*: p.kent at imperial.ac.uk*Date*: Mon, 11 Oct 1993 12:16:25 +0100

Dear MathGroup, I'm currently in a confused state regarding the use of Hold[], Evaluate[] etc. Is there a good discussion of this somewhere (apart from "Mma Book" which is a bit vague). Specifically, I have the following problem: suppose I have a string containing an expression. I want to get a exact copy of that as an expression, without any evaluation. I can do: ToHeldExpression[string] but this puts a Hold[...] around the result. I can't see any way of removing the Hold[] without the thing inside getting evaluated. On a more general level, is there a way to do an Evaluate[] to some specified level of an expression, rather than recursing all the way down? Thanks, Phillip Kent Transitional Mathematics Project Imperial College London.