New answers tagged pattern-matching
7
votes
How to define replacement rule for Minkowski inner product
Mi = DiagonalMatrix[{1,-1,-1,-1}]
Dotp[{qm[0], qm[1], qm[2], qm[3]}, {qn[0], qn[1], qn[2], qn[3]}] /. Dotp[t1_List, t2_List] :> (t1.Mi.t2)
Or
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4
votes
How to define replacement rule for Minkowski inner product
Dotp[{qm[0], qm[1], qm[2], qm[3]}, {qn[0], qn[1], qn[2], qn[3]}] /.
Dotp[a_List, b_List] :> Fold[#1 - #2 &, a b]
qm[0] qn[0] - qm[1] qn[1] - qm[2] qn[2] -...
- 19.3k
2
votes
$Assumptions = _ ∈ Reals results in incorrect simplification of ConjugateTranspose[..]
Instead of using global assumptions, use Block to define the assumptions locally, like this:
...
- 5,562
5
votes
Accepted
$Assumptions = _ ∈ Reals results in incorrect simplification of ConjugateTranspose[..]
This example is interesting. It shows us that:
Though pattern matching seems to work in $Assumption/Assumption in some cases, ...
- 55.3k
5
votes
5
votes
Accepted
Deleting list of expression by rules
You can use FreeQ to check for the existence of z in any of the expressions and filter using ...
- 27.1k
2
votes
Accepted
Replace vs. ReplaceAll involving Flat
For a way to explain the behavior, see @MichalE2's answer
The following might be a workaround, at least for the examples in the question. It is based on the observation that a catch-all rule like <...
- 27.1k
2
votes
Replace vs. ReplaceAll involving Flat
why does Replace not try the pattern f[f[x, 2y], z]?
First, I don't think ReplaceAll does ...
- 222k
6
votes
Accepted
Transforming A Complicated Expression
I don't think this is well-suited for replacement rules, since, among other things, you will have a hard time restricting the rules to only apply to entire terms (i.e. not stuff like the ...
- 27.1k
6
votes
Accepted
How to check if all elements of a list contain an expression, with 'MatchQ' or otherwise
$Version
(* "13.1.0 for Mac OS X x86 (64-bit) (June 16, 2022)" *)
In a PatternTest the test must be a boolean ...
- 126k
5
votes
Accepted
Equivalent of Nothing for patterns
You could use Repeated[..., {0,1}] to match elements which may appear zero or one times, but there's even better option in this case, that is, ...
- 15.6k
3
votes
Equivalent of Nothing for patterns
The comment section got a bit long and as it would be tedious for someone else to read through the comments I moved my last comment, that only solves this specific situation, to an answer.
I had never ...
- 1,373
2
votes
Extracting values from association via Cases
Let's say temp had a string value in there as well:
temp = <|"u" -> -5, "v" -> -5, "w" -> "a"|> -> -30
In ...
- 19.3k
4
votes
Accepted
Extracting values from association via Cases
According the the Docs for Cases,
The default value for levelspec in Cases is {1}.
You ...
- 60.3k
5
votes
4
votes
Accepted
1
vote
Clarification of the $MemberQ$
Note that there must be a space between the dot and the "1". If one copies your input, the space disappears.
Then note that "MemberQ[expression,element]" without any level ...
- 29.6k
2
votes
Translate selection from one list to another
The most minimal way -I think- to pick the even elements is to use the step specification in the Part like so:
list = {a, b, c, d, e, f};
list[[2 ;; -1 ;; 2]]
<...
- 6,579
5
votes
7
votes
Translate selection from one list to another
You could use Pick[]:
Pick[{a, b, c, d, e, f}, EvenQ[{1, 2, 3, 4, 5, 6}]]
(* {b, d, f} *)
Timing examples (numerical methods ...
- 222k
4
votes
Translate selection from one list to another
There can be many solutions, and here is one of them.
...
- 19.3k
1
vote
Accepted
Replacing a term according to a given criterion in an expression with non-commutative multiplication (for any sign and location)
For the examples
b ** (-P ** a^3) + b ** Transpose[-P ** a^3]
b ** (-P ** J ** a^3) + b ** Transpose[-P ** (-J) ** a^3]
you can try
...
- 667
0
votes
Pattern not matching BoundaryMeshRegion
As was pointed out in the comments, the reason of the no-match is, that BoundaryMeshRegion is atomic.
My ultimate goal is to change the innards of a ...
- 29.6k
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