New answers tagged variable-definitions
12
$ is probably the only non-alphanumeric ascii character without a special meaning in Mathematica and thus the only one you could use as a delimiter for various parts within a variable name.
A warning is due: Because it is so unique, it is also used internally for the same purpose, e.g. Module and Unique will generate variable names ending in $+ an ...
8
If you make any assumptions you have to share them with Mathematica as well.
For Example:
Assuming[R > 0, FullSimplify[(R^3)^(1/3)]]
(*R*)
The default assumption is that all variables are complex. (As @J.M. noted in the comments).
5
It's just not always true that $(R^3)^{1/3} = R$. How about $R=i$, for example?
N[(I^3)^(1/3)]
(* Out: 0.866025 - 0.5 I *)
If you expect this, you might have more luck with the real-valued CubeRoot function. For example:
FullSimplify[CubeRoot[R^3]]
(* Out: R *)
3
Here's something I found:
With[{h := {x = 7, y = 8}},
Block[h, x y]]
56
1
var /: Block[var, code_] := Block[{x = 2, y = 3, z = 4}, code]
So
x = 100;
Block[var, x + 2]
(* 4 *)
1
The way I prefer is
var := {x = 2, y = 3, z = 4}
ReleaseHold[Hold[Block[var, x*y*z]] /. OwnValues[var]]
x
-> 24
-> x
Or
Apply[Block, Hold[var, x*y*z] /. OwnValues[var]]
x
-> 24
-> x
For
hVars = Hold[{x = 2, y = 3, z = 4}];
We can do
ReleaseHold[Hold[Block][hVars, Hold[x*y*z]]]
x
-> 24
-> x
5
This could be another case for the injector pattern:
var = Hold@{x = 2, y = 3, z = 4}
var /. Hold[inj_] :> Block[inj, x*y*z]
(*24*)
?x
(*Global`x --- so we did not leak*)
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