Questions on expression testing and manipulation through pattern matching and constructing efficient patterns.

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3
votes
1answer
197 views

replacement rule to pull independent expression outside of Integrate

I'm trying to write a fairly general replacement rule that will pull expressions independent of the variable of integration outside of Integrate, since Simplify and ...
4
votes
2answers
123 views

Pattern matching not going over a list when using default values

if I execute the following command in Mathematica: {a,a^2,a^3}/.a^(n_:1)->b^(2 n) Mathematica returns: {b^2,b^4,b^6} ...
9
votes
1answer
223 views

CSS Selectors for Symbolic XML

Symbolic XML is a convenient way of managing XML in Mathematica, at least for casual use or small tasks. Here and elsewhere you can find examples of XML handling in Mathematica, including XSLT/XPath ...
18
votes
4answers
889 views

How to define a recursive pattern?

I want to translate this recursive syntactic definition into a Mathematica pattern1: $$ \mathtt{x}: \begin{cases} \text{Null}\\ \{\textit{integer}, \mathtt{x}\} \end{cases} $$ In other ...
21
votes
7answers
1k views

Using patterns in pure functions

Pure functions may be handy if you don't want to assign your function a name. For example I would calculate $x(x-1)$ for some numbers $x$ by ...
8
votes
2answers
501 views

Adapting “Find and Replace” functionality to work with Patterns

I was thinking if there is something like Find and Replace (Crtl+F) functionality adapted to work with patterns. Probably not, but it seems possible to create this with some effort and skills in ...
19
votes
2answers
320 views

Pattern does not match with Orderless head

Why does the following pattern matching not succeed? ...
15
votes
6answers
1k views

Finding the period of an array of integers

A simple array of integers is given. The problem is to detect if a pattern is repeatedly occurring in the array, and find the length of that pattern. For example, for ...
14
votes
3answers
393 views

Make mathematica treat $e_i^2$ as numeric

With NumericQ[symbol] = True, I can declare that a symbol is numeric. I want the expressions matching: $$e_{\text{i$\_$}?\text{IntegerQ}}^2$$ to be treated as ...
11
votes
9answers
1k views

How can a power of 0 or 1 be replaced?

Consider this given example for ReplaceAll 1 + x^2 + x^4 /. x^p_ -> f[p] This returns ...
10
votes
3answers
392 views

Patternmatching sets

How to match set-patterns against sets? A set (in the mathematical sense) is a list of elements without repetition and order of elements does not matter. For example, we have a pattern set ...
11
votes
4answers
296 views

Recognizing special cases of a defined function for permuted arguments

I have a number of ugly ways to implement the following pattern recognition task, but I'm looking for something elegant to keep my notebook tidy. I need to define a function of six variables ...
11
votes
1answer
395 views

Selectively clear DownValues

How can I clear a subset of a symbol's DownValues ? For example, suppose I have created some DownValues for $f$ like this: ...
9
votes
4answers
256 views

Pattern match for nested Association

Suppose I have Association testAssoc=Association[a->Association[1->1,2->2],b->Association[1->1,2->2]] which ...
6
votes
3answers
267 views

Converting expressions to “edges” for use in TreePlot, Graph

This question is similar to this: Nested list to graph. How to "flatten" an arbitrary expression, eg expr = a[b[c, d[e][f], g], h] to a list of key-value pairs ...
3
votes
1answer
207 views

Custom operators; custom pattern matching with pure functions

What I'm trying to achieve in Mathematica is the creation of a binary operator whose operands are both pure functions over the natural numbers. The result of the operator should be another pure ...
9
votes
5answers
446 views

How can I remove matching sublists from my list?

I want to use DeleteCases (or any appropriate function) to remove elements of a list, which in turn are lists of fixed size. The rule I wish to apply is that any ...
7
votes
2answers
147 views

How to define patterns to filter lists of replacement rules?

I have a list of replacement rules like list˘of˘replacement˘rules = {a -> 1, b -> 2, c -> 3} and I want to filter all the elements where ‘b’ is replaced ...
7
votes
3answers
551 views

Function with zero or one arguments

Is there a neat way to define a function with a single optional argument that defaults to an empty sequence? For example, suppose I want to define a wrapper for ...
6
votes
2answers
313 views

Rule for orderless function Times

I have problems extending a replacement rule. Schematically, this is the situation: I have an expression and a rule, and they work perfectly together. ...
4
votes
1answer
272 views

Convert boolean test function to pattern?

What is a "reverse" to MatchQ? MatchQ converts pattern into boolean function. So how to convert back? Suppose I want to use ...
2
votes
2answers
89 views

Strange failure of Series and Derivative

I just spend three hours and posted two Questions trying to figure something out, and it turned out all the confusion was caused by this mysterious quirk. I want to expand g[x,v] in v at v=0, using ...
2
votes
1answer
146 views

Why is there a difference when formulating patterns for Select and FirstPosition?

Select[{1, 2, 4, 7, 6, 2}, # > 2 &] Gives {4, 7, 6}. OK! So one should think that the following would work: ...
26
votes
1answer
1k views

replacement rules from a pattern and a matching expression

(This seems to be a very basic necessity in a language having pattern-matching capabilities such as Mathematica, yet I struggled for many hours to find a common solution to this problem.) Suppose ...
22
votes
4answers
1k views

Detecting patterns of black and white stones on a 2D board

I'm writing a program to play a game of Pente, and I'm struggling with the following question: What's the best way to detect patterns on a two-dimensional board? For example, in Pente a pair of ...
19
votes
2answers
359 views

What does f_[whoCalled]^:=f really mean?

I came across the following post by John Doty in this Google Groups discussion: On Friday, January 11, 2013 8:23:16 PM UTC-7, amzoti wrote: It is clear the Mathematica uses Lisp as one ...
10
votes
4answers
507 views

Building a tree

Given a list of word characters, such as this one, I'd like to build a tree, similar to this makeTree function, but with the tree in a different format. So, for an input such as ...
17
votes
6answers
857 views

Split a string at specific positions

Given a string of alphanumerical characters, how to split it simply and quickly at the center of continuous letter-substrings? Is there an elegant and fast solutions out there in the "computational ...
15
votes
3answers
420 views

Highlighting pattern strings in a large text

I would like to apply Style to strings that are matched, for example, with one or more specified patterns or regular expressions, a string or a list of both, ...
14
votes
2answers
353 views

Pattern to match L, but not L[_]

I have an expression where I want to replace L but not L[_] For example, the following doesn't work and ...
12
votes
2answers
405 views

Split a Unicode string maintaining uppercase characters

I want to split a string according to a predefined set of substrings (lowercase), though the actual text can contain uppercase characters anyplace. The task is to find the matches, longer preferred ...
11
votes
4answers
663 views

Assessing argument type in set delayed function definitions

I'm wondering how to properly assess the type of arguments passed to functions defined with :=. I want my functions to be the most efficient, unambiguous and clear ...
7
votes
3answers
247 views

Pattern matching Q for rectangular data matrices

Given a List of rectangular nx3 arrays of data, each of the form {...,{x,y,z},...}, (the ellipses are not Mathematica pattern syntax, just for illustration). Some members of this list may be - by ...
6
votes
4answers
333 views

Is there a more Mathematica-y way to label these plots?

I am studying an infinite square well in the context of quantum mechanics. ...
5
votes
3answers
958 views

position of sequence of elements in list [duplicate]

Possible Duplicate: Finding a subsequence in a list Question The position of {3, 5} is the list {1, 3, 4, 3, 5, 5, 1} is 3. How can such a position ...
4
votes
1answer
199 views

Inheritance in Mathematica using pattern matching on UpValues

Edit: I think in my original post, I missed emphasizing the main point. This is mainly a pattern matching question. If you're interested in the 'why' of this question, please read the original post ...
15
votes
2answers
2k views

Determine whether some expression contains a given symbol

Given a symbol t and an expression expr, how can I determine whether or not the symbol t ...
10
votes
2answers
326 views

Using Except with strings

Suppose that I have the following sample list, called list: list = {"bBb", "aAa", "aaa"}; Now suppose I want to select the ...
6
votes
1answer
546 views

Count sublists which match pattern

I have a list which looks like this: data={{12,0},{0,0},{20,1},{0,0}, {0,-1}}. Now I would like to count the number of sublists which: have both slots zero the ...
4
votes
2answers
79 views

MatchQ failing in some cases with Hold [duplicate]

Could someone clarify why the first of these MatchQ finds a match whereas the second does not? (I'm using version 10.0, in case that matters.) ...
4
votes
4answers
533 views

Listing matrices up to symmetry

I am interested in the equivalence relation on N x N binary matrices, in which two matrices are equivalent if one can be obtained by rotating/reflecting the other. I would like to obtain a list ...
4
votes
2answers
1k views

Classifying poker hands by pattern matching

I am working on this question posed in a Mathematica course revised in 1998. Here are the instructions: Poker Hands You are to define and show working examples of a function "...
4
votes
3answers
140 views

Extracting subscripts and superscripts

Suppose I have several types of expressions (in some random order) of the form Power[Subscript[g, a], μ] which is $g_a{}^\mu$ ...
4
votes
2answers
221 views

Alternatives ordering affects pattern matching in Cases?

Given expr = f[x, g[y], z] In the following query, the pattern h_[__, c_] appears as last slot in ...
4
votes
4answers
606 views

More elegant way

I read ReplaceOrRemoveInvalidOrMissingData Mathematica documentation, and I tried to apply the same approach to my dataset. I've got two problems, but one is only a style problem! There is one more ...
3
votes
3answers
105 views

How to apply ReplaceAll to denominator?

Here is the simple task. In reality, it's far more complicated, but it comes down to this. I want to take the expression $\frac{y}{x^2}$ and replace $x^2$ with $k$. This doesn't work: ...
9
votes
1answer
264 views

How to define function that can change patterns

Given time series data as follows: data = {{{2011, 1, 13}, 10}, {{2011, 2, 14}, 17}, {{2011, 3, 15}, 20}, {{2012, 1, 16}, 30}, {{2012, 2, 17}, 40}}; ...
6
votes
2answers
506 views

How to test whether an expression is a valid variable?

I would like to test whether an argument is a valid variable for functions like Solve and DSolve. For instance several ...
5
votes
2answers
237 views

Pattern matching deletion of list items [duplicate]

Possible Duplicate: How can I remove B -> A from a list if A -> B is in the list? I'm working toward building a graph and use some code to construct my rules which results in a form ...