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

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8
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1answer
304 views

Why does Mathematica choose the second function definition?

While working on a solution to this question I've come across a case where I simply don't understand Mathematica's behaviour. I've got the following definitions: ...
8
votes
2answers
373 views

How to Enable Syntax Coloring of Pattern Match Variable Only (i.e. Without Coloring any Associated Pattern)?

Syntax coloring for the following function definition foo[x_List] := ... will color green (and italicize by default) the argument name ...
8
votes
1answer
275 views

Mma10 mystery: Failure of pure function substitution with Interpretation?

Bug introduced in 10.0.0 and fixed in 10.0.1 I had code to display with subscripts from Displaying index as subscript on output: e.g. C[i] -> C_i with Notation[...] or Interpretation[..]? which ...
8
votes
1answer
245 views

Creating a version of SequenceAlignment that accepts patterns

SequenceAlignment seems like a function that is not (yet?) fully integrated into Mathematica. I want a function that accepts general patterns instead. I ...
7
votes
5answers
360 views

Splitting strings at lower case characters and numbers

I'm trying to split the strings of chemicals into their elements and numbers. See this example "Fe3O4" will be split into ...
7
votes
3answers
224 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 ...
7
votes
2answers
211 views

Why does the name of a pattern affect the result of a transformation rule?

I was playing a little dirty, trying to get a template for defining a Curl[] operator. I wrote the following rule, which I knew was going to spit out a few ...
7
votes
2answers
218 views

Using MatchQ (or other means) to parse an expression using sums of COS or SIN correctly

I am writing a function that will take an expression as input. I want to make sure the expression is valid first before processing it. Looking for a correct to use ...
7
votes
4answers
558 views

How to collect terms with positive powers in polynomial

I am trying to collect all terms with non-negative powers of $x$ in polynomials like $\frac{1}{x^2}\left(a x^2+x^{\pi }+x+z\right)^2$ First expand the polynomial ...
7
votes
1answer
219 views

Is it possible to specify a context-sensitive, “depth-agnostic” rewrite rule?

I'm using the term "depth-agnostic" in this post to describe structural patterns featuring a "target" sub-pattern that can occur "at any depth" relative to one or more "context" sub-patterns. As a ...
7
votes
3answers
158 views

Checking through an expression

I am writing a code that manipulates expressions that contains functions with an arbitrary number of arguments. An example expression is ...
7
votes
1answer
253 views

How does Mathematica wrap code for front-end needs? Why does this wrapping affect the evaluation?

Mathematica wraps any expression with some boxing code before showing the evaluation result in the front-end. Unfortunately, the wrapping algorithm and its position in the Mathematica end-to-end flow ...
7
votes
1answer
208 views

Built in way to de-list singletons?

Is there a built in method to de-list singleton expressions, like this rule-based solution: expr_ :> If[Length[expr] == 1, First@expr, expr] In data ...
7
votes
1answer
718 views

Extracting coefficients from a partial differential equation

Frequently, I come across the following problem: How to rewrite a complicated partial differential equation in a more clear way? I would like to create some order by collecting terms that are equal. ...
6
votes
5answers
391 views

The correct pattern for Cases

I have a problem that, admittedly, I have already solved using Select instead, but it is irking me that I cannot seem to construct the right pattern to solve it ...
6
votes
5answers
308 views

Find patterns in a list

again, I have a list like this: ...
6
votes
4answers
284 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. ...
6
votes
2answers
218 views

Is it possible to use PatternTest and Optional value on one Pattern simultaneously? [duplicate]

Possible Duplicate: How to Combine Pattern Constraints and Default Values for Function Arguments First a simple example: define a function "add" with two arguments, and its second argument ...
6
votes
4answers
284 views

How to match a sequence of complex patterns?

I have list with the form {{a1,b1}->{x1,y1},{a2,b2}->{x1,y2},...} where the {ai,bi}'s can be ...
6
votes
2answers
265 views

Fastest way to test if a numerical array has complex elements

I am looking for the fastest way to test whether an n-dimensional numerical (NumericQ) array (in the ArrayQ sense) is complex or ...
6
votes
3answers
345 views

Replacement rule only matches part of expression

I have the result of a calculation (which is too long to mention here) and it gives ...
6
votes
3answers
201 views

Problem with WordBoundary in string patterns

I am trying to extract from a string all words that end with "-man", but the problem is that WordBoundary does not seem to work as it returns whole string ignoring ...
6
votes
4answers
504 views

Function argument to default under certain condition

Inspired by this and this question (and how I handle this in practice), what is the best way to default a function value when a certain condition is met? For example, if a function is defined as: ...
6
votes
3answers
177 views

Using PatternTest and/or Condition to detect equal list lengths as well as list element formats

On searching Mathematica.SE for information about overloading functions, I came across several threads about PatternTest and ...
6
votes
3answers
172 views

Isolating string characters

I have the following string: ...
6
votes
2answers
291 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. ...
6
votes
3answers
122 views

Pattern matching: Times[a_] vs Times[a__]

I don't understand why MatchQ[ HoldComplete[Times[3, 2, 2]], HoldComplete[Times[a_]] ] is returning True. I thought that ...
6
votes
2answers
149 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
3answers
174 views

Strange behavior of MemberQ, Position

After importing an array of latitudes and longitudes and trying to find the position of some latitudes I was encountered with an unexpected problem since certain values could not be found for some ...
6
votes
2answers
248 views

Formatting text through pattern matching

I am trying to format some text based on some patterns. ...
6
votes
1answer
216 views

Match sequence of zero or more characters except a given character

This looks like it should be simple: I want to match an "i" followed by an "o" with an arbitrary (possibly zero-length) sequence of characters in between, unless that sequence also contains an "i". ...
6
votes
2answers
99 views

Unexpected result from StringReplace

The following works as expected. StringReplace["xxxyxz", "x" ~~ _ -> "ww"] "wwwwww" And so does this. ...
6
votes
1answer
421 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 ...
6
votes
2answers
214 views

Variable scoping problem when mapping over delayed replacement

This is something that got me curious while I was playing around with Mathematica. Consider the following (contrived) example: ...
6
votes
1answer
237 views

How to set up new types for pattern matching strings?

Consider the following toy example: I have a set of language sounds, which I partition into two exclusive subsets, consonants and vowels. I want to set up string patterns for e.g. ...
6
votes
1answer
76 views

Held keys in associations

Jacob Akkerboom commented: Note that PositionIndex does work correctly with held expressions, whereas this is a bit painful to implement using ...
6
votes
1answer
300 views

Pattern matching in subscripted variables

I am trying to use subscripted variables as symbols and provide assumptions elegantly for them, e.g. in order to simplify logs, I'd like to have ...
6
votes
1answer
216 views

Pattern definition for replacing plus and subtract

Suppose I have two functions $h_1(x)$ and $h_2(x)$, for which we know their sum and their difference: $$ h_1(x)+h_2(x) = d(x) \qquad h_1(x)-h_2(x) = i f(x) $$ I have a complicated expression, in ...
5
votes
5answers
479 views

How can I use nested conditionals inside my functions?

I'm a big fan of using conditionals inside my functions to deal with cases, that is, to pattern match in stages and possibly leave a function unevaluated. ...
5
votes
3answers
493 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 ...
5
votes
2answers
228 views

Unexpected behavior of rule matching a pattern

I am a beginner exploring the world of Mathematica. I expected the following code T[6, 5, 4, 1, 2, 3] /. {T[a___, 1, b___] -> Length[List[b]]} should return ...
5
votes
2answers
178 views

Extract substring by repeated StringPattern

This code failed, but may exemplify my intention. StringCases["aA1bbbbbbbbbbaA2baA3b...aA4b",Repeated[Shortest["a"~~xx__~~"b"],{2,100}]] I want to get the ...
5
votes
4answers
238 views

Pattern matching - comparing two lists

I would like to compare two different lists to see if the shorter one is a member of the larger e.g. is the list {2,3}, with that sequence of elements, a member of {1,2,3,4,5}? I have tried using ...
5
votes
3answers
181 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 ...
5
votes
2answers
208 views

How to get complement of a pattern

I have a list. I want to get all the elements in that list which do not match a given pattern. That is, I want the strings which do not match any of the following patterns: First and last characters ...
5
votes
4answers
193 views

Extracting sequences from a list?

Suppose I have a list of arbitrary length like {1, 2, 3, "Open", 3, 2, "Close", 9, 3, 4, "Open", 1, 0, "Close", 3, 5} and I am trying to extract the sequences ...
5
votes
1answer
132 views

Sentiment analysis of tweets

I want to use Mathematica for a sentiment analysis on tweet-messages. For that purpose i selected several tweets. Each tweet is interpreted by myself as positive (pos) of negative (neg). For example: ...
5
votes
2answers
282 views

Keep Ordering of Bra Ket When Printing

I would like to keep the ordering of the bra ket-print but right now this doesn't happen. Any Idea? I tried playing with HoldForm but then i could evaluate the expression inside properly ...
5
votes
3answers
326 views

Highlighting text with StringReplacePart but also using Style, Subscript

For a Natural Language Processing analysis task it's desirable to highlight a text string programmatically according to XML tags that reference specific words or phrases. The XML tags specify the ...
5
votes
2answers
221 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 ...