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

learn more… | top users | synonyms (1)

5
votes
3answers
296 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 ...
10
votes
1answer
299 views

Mixing patterns with string patterns

I have imported an XML document into Mathematica. It is now represented as Symbolic XML expression in the variable xml: ...
9
votes
4answers
549 views

Using Position (which requires a pattern) in the same manner as Select (which requires a criterion)

I am using Mathematica7. I have a list of lists (creatively named list in the following sample code) containing data. I would like to find the positions of the ...
5
votes
2answers
213 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 ...
6
votes
2answers
281 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. ...
11
votes
2answers
314 views

Should I use \\\“ or \” to match " in regex?

Both of the following return True: ...
2
votes
2answers
294 views

Pattern test for variables during function definition

I am having a problem with pattern testing on variables during function definition ...
4
votes
2answers
228 views

Formatting text through pattern matching

I am trying to format some text based on some patterns. ...
16
votes
2answers
901 views

How do I perform string matching and replacements?

What are, and how do I use Mathematica's string matching and replacement tools?
16
votes
5answers
2k views

The difference between 0. and 0

I have a function for which 0 is a special case: f[A___, 0, B___] := 0 But since I am doing numerics, sometimes in the course ...
11
votes
4answers
462 views

Calling Table with custom iterator

I often find myself in situations where I, for example, need to build a table for some expression, but want to set the number of points rather then the step size, so the code ends up looking like this ...
5
votes
5answers
416 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. ...
16
votes
4answers
431 views

Splitting a list

Please consider the following list: data={1, 0, 0, 0, 2, 5, 2, 3, 0, 0, 3}; Now I would like to split the list into 0-sequences and Not-0-sequences as following: ...
7
votes
3answers
221 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 ...
3
votes
1answer
141 views

Set promotes Rule to RuleDelayed?

In mentally building a model of how Mathematica works, I naively expected Set to create a Rule in a symbol's ...
8
votes
1answer
236 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 ...
4
votes
1answer
155 views

Searching Notebooks for String Patterns using Workbench v2

The Workbench webpage describing new features in version 2 lists the ability to "Search notebook documents with the Mathematica pattern search utility" under the heading Mathematica Front End ...
15
votes
2answers
455 views

Pattern issues weird warning

Take for example head[b_[PatternSequence[_, _]]] := 9 I know this example serves no purpose as is. It also happens in useful examples such as ...
14
votes
3answers
238 views

What's wrong with this pattern of the form Except[Repeated[…]]?

I'm trying to build a head that recognizes molecules. Here's the code ...
11
votes
3answers
511 views

Delete duplicates in a list, depending on the sequence of numbers

Below, list is a representative sample of my list, which contains lists of integers. I would like to be able to input: ...
2
votes
2answers
106 views

Using FreeQ with implicit functions

In Mathematica 7, I want to determine whether a list of free of numbers greater than 1 or not. It seems like using FreeQ would be a concise way to do this: ...
16
votes
1answer
455 views

NotebookFind and String Pattern Expressions

Is there a way that NotebookFind can be used to match string pattern expressions rather than just strings? The documentation for ...
0
votes
1answer
431 views

What does the slash-colon symbol do?

I came across a bit of code that uses the syntax /: and I don't know what it does. I can't find its documentation, or maybe I'm just not looking properly. The code ...
15
votes
2answers
416 views

Successful match in Replace but not in Cases?

I have a little example that exhibits a successful pattern match in ReplaceAll that Cases misses and I wonder if the assembled ...
8
votes
2answers
365 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 ...
15
votes
1answer
678 views

How to Combine Pattern Constraints and Default Values for Function Arguments

EDIT: As several respondents have noted in the answers and comments below, the original example had a default value that would never be used because of the way patterns and default values are ...
16
votes
1answer
316 views

Is pure pattern matching without PatternTest and Condition Turing-complete?

Note that this question is not a duplicate of that one. It is specifically about the pattern-matching engine, and explicitly excluding those patterns which call back into the full evaluation (i.e. ...
8
votes
1answer
264 views

Does Mathematica use first order or second order order unification?

When Mathematica is pattern-matching expressions, does it use first order or second order unification. Just to clarify the difference between first order and second order unification: In Second order ...
8
votes
1answer
200 views

MatchQ and patterns for similar lists

I can't seem to find the right set of patterns to independently match two different lists. Simplified versions of the lists are as follows: ...
8
votes
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: ...
10
votes
6answers
295 views

How can I mix the behaviors of StringReplace and ReplaceAll in a single rule?

I'm trying to take a list of the form { {"65 + 3 months", 75}, {"65 + 4 months", 75.1} }, and transform the string part to a number such as 65.25 or 65.333, ...
9
votes
3answers
246 views

Splitting a list in which figures vary from negative to positive

Consider the following list: data={4078, 256, -1266, -388, 1290, 1368, 1446, 1524, 2}; I would like to split any kind of such list always, when figures turn form ...
6
votes
4answers
268 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 ...
9
votes
2answers
230 views

Why doesn't Cases match all instances of XMLElement, given Infinity levelspec?

Why doesn't Cases match all instances of XMLElement, given Infinity levelspec? ...
4
votes
1answer
227 views
12
votes
2answers
334 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 ...
-2
votes
1answer
206 views

How to set a rule in pattern matching to change a string from one form to another

I want to define a rule that will change a particular type of string to another form. For example:- a string having ...
4
votes
2answers
292 views

Why can't NumberQ be used as the head of a pattern?

Consider the following: list={1/First[{}], 1, 2, 1/First[{}], 3}; DeleteCases[list,_NumberQ] I wanted to remove all cases, which did not match ...
22
votes
5answers
1k views

Fetching data from HTML source

I want to generate a couple of plots/graphs with Area51 statistics. Since Area51 doesn't work with the SE API, I'm forced to find another way to get the information I want. That other way is with ...
4
votes
1answer
299 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
102 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
896 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
695 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 ...
40
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
683 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
742 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
548 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
225 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
675 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 ...