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

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4
votes
1answer
301 views

Path queries for tree-structured data

Can anyone suggest documentation or tutorials for developing path queries and indices for (XML-like) tree-structured data? Suppose data is organized hierarchically in key->value pairs, eg: ...
4
votes
1answer
103 views

How do you set an Optional parameter with a global variable on a Function defined in a Package

In a Package I am writing, I'm trying to define a function with an Optional parameter in it that is set to a global variable. ...
15
votes
6answers
911 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 ...
17
votes
6answers
704 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 ...
41
votes
1answer
1k views

How to generally match, unify and merge patterns?

This question was split from this one. While that question is now about how to match two particular patterns (mostly using Verbatim or ...
15
votes
2answers
715 views

How to use subscript in pattern names?

For example I want to define a function with parameters σx and σy, that is, the function will be declared as: f[σx_,σy_] := . . ...
15
votes
4answers
777 views

How to match a pattern with a pattern?

UPDATED This question is about: "What is the pattern to match a pattern-definition, exactly as it is written?" My original question is now split according to Mr.Wizards insightful answer below. This ...
17
votes
2answers
566 views

How to inject an evaluated expression into a held expression? [duplicate]

I know that there are methods to structurally manipulate held expressions (discussed e.g. here), but I failed to apply those for this particular problem: ...
0
votes
1answer
177 views

How to use Function[] in MatchQ[] and control argument's evaluation? [duplicate]

Possible Duplicate: Why doesn't PatternTest work with Composition? ...
6
votes
1answer
233 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. ...
8
votes
2answers
689 views

Mathematica rule substitution memory

First I present the specific programming question, and then I provide further background details. Given an expression in Mathematica, say f=3x+7y, there are two ...
7
votes
1answer
692 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. ...
36
votes
9answers
1k views

Injecting a sequence of expressions into a held expression

Consider the following toy example: Hold[{1, 2, x}] /. x -> Sequence[3, 4] It will give Hold[{1, 2, Sequence[3, 4]}] ...
10
votes
3answers
787 views

Passing down arguments

In R, one can use ... to pass arguments down to another function. For example ...
44
votes
4answers
2k views

Using a PatternTest versus a Condition for pattern matching

My last question to the site resulted in several answers that involve using pattern matching in Mathematica, a feature I wasn't very familiar with at the time. I am currently reading Mathematica ...
20
votes
1answer
429 views

Why doesn't PatternTest work with Composition?

While playing around with the solutions to this question, I've found some very strange behaviour: ...
6
votes
3answers
328 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 ...
8
votes
4answers
273 views

Check in a series if there exists adjacent values with less than a certain number of missing values

I'm working with a large number of series of different experiments, where there exist a lot of experiments where there are no entries. I now want to draw a sample where there should exist at least ...
19
votes
2answers
1k views

Pattern to match a non-empty list of non-empty lists

Is there a pattern to match a list of lists, containing at least one list, with each list containing at least one element? In the Mathematica documentation it says that the pattern ...
23
votes
2answers
432 views

How can I ensure that I am constructing patterns in the most efficient way possible?

Inspired by this answer, I am interested to know if there are best practices or rules of thumb for constructing patterns, for example for use in function definitions (...
47
votes
4answers
1k views