Tagged Questions

Questions about Mathematica's predicate functions.

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8
votes
0answers
78 views

A bug in the overloading of MemberQ and FreeQ for Association?

While answering Pattern match for nested Association I came across behavior of MemberQ and FreeQ in 10.0.1 that I believe is ...
14
votes
2answers
394 views

Better way to test that a matrix is upper-triangular?

Today, I got to thinking about how to test that a matrix was upper-triangular. So I had a try at it. Algorithm $\quad \quad a_{ij}=0 $ Or $i \leq j$ $\Rightarrow$ $True$ My solution is ...
3
votes
1answer
96 views

Why does pattern test not work in this case to restrict the function parameters?

I was looking at this Q&A about using pattern test (pattern_?test) vs pattern condition (pattern_/;cond) and came across ...
3
votes
2answers
182 views

Finding similar expressions in list

I have a function that returns to me lists of expressions, like: ...
2
votes
2answers
103 views

Testing for arbitrary algebraic expression in given variable

I want to test, for example with MatchQ, if the argument of a function is an arbitrary expression in a single or several variables whose names can be assumed to be ...
7
votes
3answers
155 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 ...
6
votes
2answers
231 views

Why does PolynomialQ[x^n, x] return False?

From what I can see PolynomialQ will return False whenever some exponent is another variable such as here: ...
1
vote
2answers
500 views

Faster way to test if an expression equals zero

I want to test if expressions (mix of variables, functions and numbers) are zero valued, as fast as possible, and PossibleZeroQ is sometimes very slow. One solution ...
1
vote
2answers
200 views

How to pick a solution from a list of solutions using a test?

I have a list of solutions that depends on a parameter b3 and I'd like to get the solution for which the x value is minimal when ...
12
votes
2answers
176 views

How can one write a robust ListableQ function?

I would like to have a test that determines if a particular function is Listable. In the case of Symbols this is merely a matter of checking Attributes. ...
4
votes
1answer
114 views

How can I test properties of a symbol without unwanted evaluation

Problem How to get the head, size, dimensions, etc. of a symbol without evaluating it? Since Mathematica does not allocate fix storage space and type to symbols it is not trivial to query runtime ...
4
votes
1answer
239 views

How to check if a given expression is an “explicit algebraic number”?

The documentation for PossibleZeroQ says: With the setting Method...
2
votes
1answer
150 views

How to work with the symbol EndOfFile? [duplicate]

How to work with the symbol EndOfFile? I want to use the EndOfFile symbol to determine when my control structure reaches the end ...
15
votes
5answers
1k views

How to check if an expression is a real-valued number

What is a simple, fast way to test whether an expression is a real-valued number? I ask since there is no RealQ function. If we call this test ...
15
votes
1answer
573 views

_?NumericQ equivalent for lists

A few months ago I got a simple answer (see: 1 ) to the question of how to force numeric evaluation during use of functions such as NMinimize - namely the use of _?NumericQ in the argument list. I ...
5
votes
2answers
307 views

Why is an integer not considered as a real?

Please consider the following: zeros={0.,0}; data={1, 0., 0}; DeleteCases[data, #]&/@zeros Head/@zeros (*{Real, Integer}*) (*{{1, 0}, {1, 0.}}*) For my ...
5
votes
1answer
121 views

lists of conditions

I have got coordinates in two list of Latitude and Longitude and would like to check if those coordinates are in a certain grid Example lists are: ...
8
votes
2answers
494 views

How does Mathematica decide that Log[2,8] is integer?

At school we learned that $\log_b(x)=\log(x)/\log(b)$, which is implemented in Mathematica as Log[b, x], but the results are different. ...
0
votes
1answer
59 views

What is the most elegant way to see if an expression is affected by a certain symbol? [duplicate]

Possible Duplicate: Determine whether some expression contains a given symbol Let's say I have some expression: sample = {1, 1/q, f[m]} And I want to ...
10
votes
3answers
457 views
16
votes
9answers
1k views

How do you check if there are any equal arguments(even sublist) in a list?

I would like to set up a function which has to return True if at least two arguments of a given List are equal. So if I give {1,4,6,2} to the function it has to ...
2
votes
2answers
107 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: ...
11
votes
1answer
250 views

Why does Assuming[x > 0, TrueQ[x > 0]] return False?

Assuming[x>0,TrueQ[x>0]] should, as I understand it, test TrueQ[x>0] after assuming ...
18
votes
2answers
464 views

Implementing a safe ValueQ that does not evaluate its argument

Mathematica has a built-in function ValueQ. Quoting the docs, ValueQ[expr] gives True if ...
18
votes
4answers
714 views

Why does Mathematica claim there is no even prime?

I wonder if this is a bug, or if I'm misunderstanding something: Exists[n, EvenQ[n] && PrimeQ[n]] // Resolve (* ==> False *) So if I interpret this ...
12
votes
5answers
1k views

Fastest square number test

What is the fastest possible square number test in Mathematica 7, both for machine size and big integers? I presume in version 8 the fastest will be a dedicated C LibraryLink function.
14
votes
3answers
230 views

How can I test properties of a symbol from the string name without the symbol completely evaluating

Suppose I have a few symbols, one of which has a value: {abc1, abc2 = 5, abc3}; I can use Names to get the list of names, as ...