# Tag Info

### How can I adaptively simplify a curved shape?

We can use the Ramer-Douglas-Peucker algorithm to reduce the number of points. This algorithm was originally devised for processing map data. ...
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### Why does removing a function and defining it on the same line not work?

Executing Trace on an expression reveals what is actually happening: ...
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You are looking for $NewSymbol which is run every time a new symbol is created. For example, let say you only want x, ... • 34.1k 19 votes Accepted ### How can I obtain a complete list of the kinds of atomic expressions in the Wolfram Language using only the language itself? You can use EntityValue to find out what symbols can be atomic: ... • 131k 16 votes Accepted ### When is a symbol a Symbol? Is there an easy Mathematica way to test if an object is a symbol sort of like a SymbolQ? I'd probably use x_Symbol in a function argument to control evaluation. Otherwise, one might do the following (thanks to @Leonid for pointing out an oversight). If ... • 240k 14 votes ### Why did Mathematica choose brackets for function arguments over parentheses? Although Chip's answer already suffices to address the question, I would like to quote here a relevant part of the dialog by Theo Gray and Jerry Glynn in their book Exploring Mathematics with ... 14 votes Accepted ### How to make Mathematica variables declarative instead of just-in-time? Edit: method extended for multiple contexts and unlocking mehtod added. Let's protect whatever is a new symbol. In old answer I've manually excluded symbols matching ... • 137k 13 votes ### Generating list of alphabet letters Nowadays, one can use Alphabet[] along with Take[] or Part[] + ... 13 votes ### How can I define symbols but not have them show up in the front end? Core Function Here's a single function that does all this coloring stuff: ... • 47k 13 votes Accepted ### Why does args symbol exist in a fresh kernel? It's a type of otherwise harmless bug that tends to come and go with versions. I would suggest to report it to Wolfram, but also not to worry about it. Notice that the symbols have no associated ... • 236k 13 votes ### What does$ mean in an output?

This usually means you've exported a local symbol from the context in which it was localized. Consider: Module[{x}, x] (* x\$24939 *) Your results may vary. The <...
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### Bug: With[] pattern-variable renaming misses symbols within Except

I agree that this is a bug. However, I want to point out that this usage of Except does not seem to be allowed in older versions. In version 9.0: We don't get the ...
• 236k
Accepted

### Defining a symbol e that represents plus-minus-one, so that e^2 == 1 and e^3 == e

A quick way is to use TagSet[] and TagSetDelayed[] to teach Power[] how to deal with your ...
Accepted

### How to list all user-defined symbols?

User defined symbols/functions are in the Global context: a = 1; b[x_] := a x^2; c[x_] := f[x]; Names["Global*"] {"a", "...
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### PlusMinus definition unexpectedly affects plotting

It appears that PlusMinus is the only wrapper that is not Protected: ...
• 272k

### When is a symbol a Symbol? Is there an easy Mathematica way to test if an object is a symbol sort of like a SymbolQ?

How about: SymbolQ[_Symbol] = True SymbolQ[_] = False ?
• 13.9k
Accepted

### Equivalent for \hookrightarrow, ↪

You can use an empty TemplateBox to create a new operator. For example: ...
• 131k

### How can I adaptively simplify a curved shape?

Here is my attempt to use ParametricPlot for obtaining an adaptive approximation of the shape. It is based on the code of glyph to ...

### How can I adaptively simplify a curved shape?

Here I present a very simple angle-based polygon reduction algorithm as described in the chapter "A Simple Algorithm" of David Eberly's "Polyline Reduction". The only addition is ...
Accepted

### 1 is not the SameQ as Null, but why might 1 be Equal to Null?

=== (SameQ) tests structural equality and is meant mainly for programming uses. Like nearly all functions named as ...
• 236k

### How can I implement a listener variable in Mathematica?

As part of handling this for myself I wrote a package that does it. The idea was to mimic the *Var() classes in tkinter. I'll do ...
• 47k
Accepted

### Change nested list of symbols to nested list of numbers

symbols = {e4, {e200, {e1, {e11, e23}}}}; Map[FromDigits@StringDrop[SymbolName[#], 1] &, symbols, {-1}] {4, {200, {1, {11, 23}}}} ...
• 399k

### Make symbols atomic, without losing their type

Perhaps what you want is symbolic tensors: http://reference.wolfram.com/language/tutorial/SymbolicTensors.html ...
• 236k
Accepted

### Make symbols atomic, without losing their type

You could use my TensorSimplify package help with this. Install the paclet with: ...
• 131k

### How to generate a horizontal histogram with words?

First of all, you don't need a Histogram, you need BarChart. Secondly, you need to massage the data slightly so each data point ...
• 67.5k
Accepted

### Why does removing a function and defining it on the same line not work?

I use the word internal symbol rather than just symbol, to make it easier to distinguish between the name of a symbol and the internal representation of the symbol inside the kernel. I felt I should ...
• 12.2k
Accepted

### Check if symbol is in core language

You can look it up using WolframLanguageData, which has a list of all pre-defined symbols: ...
• 70.9k
Accepted

### Implement abstract algebraic structure

I decided it was worth giving another example of modern OOP in Mathematica. There will be a small amount of code, but almost all of it is boiler-plate. I use a package to handle most of the boiler ...
• 47k