Linked Questions
32 questions linked to/from Unexpected behavior of rule matching a pattern
4
votes
1
answer
157
views
How can I avoid this ReplaceAll trap? [duplicate]
I am having some difficulties with the ReplaceAll function.
When I write:
{1, 2, 3, 4, 5} /. x_?OddQ -> x^2
I expect:
<...
- 129
1
vote
2
answers
258
views
Why doesn't ToString work in ReplaceAll? [duplicate]
I'm trying to use ReplaceAll in a subscript. However, it doesn't seem to work as expected if I want to use the output the subscript in a ...
- 1,870
5
votes
2
answers
161
views
Trouble with Replacements [duplicate]
I have the following line of code:
Plus @@ Table[p[x], {x, 0, 20}] /. p[x_] -> Boole[MemberQ[{0, 5}, x]]
The first part of this produces
...
- 249
1
vote
2
answers
236
views
Make a partition with a rule [duplicate]
I wrote this line of code :
{{1, 1, 1}, {1, 1}} /. ((x___ /; Length[x] > 2) -> Partition[x, 2, 1])
generates this error :
Partition::pdep: Depth 1 ...
- 616
2
votes
1
answer
119
views
Rule vs RuleDelayed in the context of StringReverse [duplicate]
{"test", 3} /. s_String :> StringReverse[s]
{"test", 3} /. s_String -> StringReverse[s]
The second line gives the error:
StringReverse: String expected ...
- 2,311
3
votes
1
answer
138
views
How to localize symbols on the right-hand side of Rule when using ReplaceAll? [duplicate]
I am frustrated by the following:
{1, 2, 3.0} /. a_Integer -> a + 1
The a on the left side of the arrow is localized and ...
- 48k
1
vote
1
answer
161
views
How to use EvenQ[] in patterns? [duplicate]
This works:
(w[1] + w[2] + w[3]) /. w[s_] -> If[s == 2, w[s], 0]
(* w[2] *)
This doesn't:
...
- 4,553
1
vote
0
answers
248
views
Problem in evaluating nested anonymous functions [duplicate]
It seems that I have found a bug (or a fundamental problem in the design of the programming language of Mathematica) with functions defined as rules.
Define the function g as g(1)=2 and g(2)=1. We can ...
0
votes
1
answer
152
views
Sum of Sequence inside a replace rule? [duplicate]
I'd like a replacement rule that replaces derivatives with their total order. I tried
ReplaceAll[Derivative[x__] -> Plus[x]][Derivative[1, 1]]
but it doesn't ...
- 330
0
votes
1
answer
80
views
What's wrong with my rule? [duplicate]
Consider a simple code to form a SparseArray:
Q = 5;
a = Table[i, {i, Q}];
SparseArray[{{j_} /; j > 2 -> a[[j]]}, {Q}]
Part::pspec: Part specification j ...
- 352
1
vote
1
answer
54
views
Replacing with Elements from a List [duplicate]
I have a fairly complicated expression with nested lists and I want to substitute a given string for each integer. Here's a simple example where ind is my integer-valued data structure and names is ...
- 68.3k
2
votes
0
answers
59
views
pattern matching and applying a function, not working as expected [duplicate]
Consider the following code
G[x, y] /. a_[b__] -> Total[a @@@ Permutations[List[b]]]
I expect it to give
G[x, y]+G[y,x]
...
1
vote
0
answers
41
views
Replace date pattern [duplicate]
I have a list, such as the following:
li = {"2017-10-16", 10.24, 10.71, 10.18, 10.61, 10.61, 16802200}
Extracting the first element ...
- 259
0
votes
0
answers
38
views
Manipulating named patterns inside replacement rules [duplicate]
When I evaluate the following expression,
{a -> "value1", b -> "value22"} /. {Rule[x_, y_] -> Rule[x, y]}
I get ...
- 1,287
0
votes
0
answers
36
views
Puzzling transformation rule output [duplicate]
My problem should be a trivial one but for the life of me I can't get it to work.
This is my data (10 rows, each made up of a DateList and a list of 5 numeric values corresponding to that date);
<...
- 790