Defining constants inside a script?

Question

At the beginning of my script, I define a constant E by writing E:=2u+2uv, but then at the end of the script after running the final command, the result comes out with the form K/(2u+2uv). My question is simple: how do I make Mathematica recognise that the result should be in the form K/E?

I don't understand the question. If you do not want 2u+2uv to be substituted for E, why are you defining E:=2u+2uv — bill s, Feb 06 '17 at 18:25
I mean 2u(1+v), which is 2u+2uv. And I've tried changing the symbol to a lower case e to avoid the confusion with the built-in E, but I get some strange error:
Tag Plus in 2u+2uv is protected — Damien Clarke, Feb 06 '17 at 18:44
What you are trying to do is achieved through Simplify and similar commands, and not through defining a value for e. For instance, see the following: Simplify[k/(2 u + 2 u v), e == 2 u (1 + v)] returns k/e, which I think is what you want. Note also the important fact that uv is DIFFERENT from u v (notice the space, which is interpreted as multiplication). The first is a single variable named $uv$, the second is the product of $u$ by $v$. If you want to be extra explicit, you can also use * to indicate multiplication. — MarcoB, Feb 06 '17 at 19:57

score 2 · Answer 1 · answered Feb 07 '17 at 01:12

Let's take the expression that you have at the end of the script

K/(2 u + 2 u  v)

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and look at it using FullForm. Looking at expressions using FullForm is a good way to figure out how to perform replacements or substitutions.

FullForm[K/(2 u + 2 u  v)]

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We will take the portion enclosed by Power and attempt to replace it (/. is a shortcut for ReplaceAll) with the symbol e.

K/(2 u + 2 u  v) /. Plus[Times[2, u], Times[2, u, v]] -> e

(* K/e *)

This produces the desired result.

So you can place this at the end of your script.

If you are still struggling, kindly place your actual code in the question and you will doubtless get an answer that fits your needs.

Defining constants inside a script?

1 Answers1