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Questions tagged [expression-test]

Questions about Mathematica's predicate functions.

18
votes
6answers
3k views

Fastest square number test

What is the fastest possible square number test in Mathematica, both for machine size and big integers? I presume starting in version 8 the fastest will be a dedicated C LibraryLink function.
1
vote
1answer
45 views

How does one test whether or not an integration has succeeded?

This must be a very simple matter--but how to address it eludes me at the moment. I have a series of integrands--and want to flag whether the symbolic integation has succeeded or not (in order to ...
14
votes
1answer
142 views

Why is IsomorphicGraphQ so very slow (in this instance)

Bug introduced in 10.0 or earlier and persisting through 12.0.0 Can someone explain why the following code does not complete within a reasonable time? ...
22
votes
2answers
1k views

Why no RationalQ or RealQ?

Interesting pattern came up as I go through the homework replies of my students. Why is there no RationalQ or RealQ? We have <...
3
votes
1answer
74 views

How to prove a numerical identity?

Let be a function power function f[s_, r_] := Piecewise[{{s^r, s >= 0}, {0, True}}]; And its convolution ...
0
votes
1answer
30 views

Testing which expression is greater

I have two expressions: expr1 = e^2/(8 + 4*e + e^2) and expr2 = (d^2 - 2*d*e + e^2)/(8 + d^2 - 2*d*2 - 2*d*e + 4*e + e^2) ...
8
votes
4answers
708 views

How to check is there any negative term in a large list?

I want to check if a data set of size $10^{10}$ contains any non-positive elements. Positive[Name of dataset] returns a list of ...
9
votes
1answer
115 views

Ordering real numeric quantities

Suppose I want to have a function (call it NLess) that given two real numeric quantities, a and b, it returns True if a is smaller than b, ignoring precision. Here are some test cases: ...
8
votes
1answer
287 views

Is there a defined priority for pattern matching?

If you define a function g, like so: g[x_?EvenQ] := "even" g[x_?NumberQ] := "number" why will Mathematica always return ...
5
votes
1answer
578 views
4
votes
2answers
292 views

Check if number is irrational/transcendental

Mathematica provides functions to test whether a number is an integer, even or odd, prime, rational, real or complex. However, I could not find any explicit way to determine whether a number is ...
3
votes
3answers
78 views

How to check expression depends on symbol in a particular way

Consider these two expressions: expr1 = a d g[X, c]^2 + e g[X, f] + 3 expr2 = a d g[X, c]^2 + e X + 3 How do I check whether these expressions depend on ...
23
votes
1answer
293 views

Which second arguments is VectorQ/MatrixQ/ArrayQ optimized for?

VectorQ and similar functions (MatrixQ, ArrayQ) treat certain second arguments specially. ...
2
votes
1answer
35 views

Symbolic variable for If argument [duplicate]

i want to realize an if in this way : var=expression; If[var==0, Print[Hello]]; If[var!=0, Print[Hey]]; The system doesn't know if ...
11
votes
2answers
349 views

About shorthand notation for conditional pattern (Paul Wellin “Essentials of Programming in Mathematica”)

I am reading Paul Wellin's "Essentials of Programming in Mathematica". Mr. Wellin wrote the following in his book: There is a convenient shorthand notation for conditional patterns that is ...
17
votes
7answers
1k views

How to check if a vector is an eigenvector of a matrix using mathematica?

Here is a vector $$\begin{pmatrix}i\\7i\\-2\end{pmatrix}$$ Here is a matrix $$\begin{pmatrix}2& i&0\\-i&1&1\\0 &1&0\end{pmatrix}$$ Is there a simple way to determine ...
26
votes
4answers
562 views

Is there a GraphicsPrimitiveQ (or a complete list of Heads of graphics primitives)?

For various reasons related to workflow associated with creating figures for journals, I am creating functions that will accept graphics primitives and a set of options and spit out a ...
11
votes
2answers
2k views

Evaluating an If condition to yield True/False

I would like to decide whether an option passed to my custom function has the value Automatic or something else. This is my attempt: ...
0
votes
0answers
15 views

I want to extract coefficients of a linear formula. But my code didn't work [duplicate]

I want to extract coefficients of a linear formula and I wrote the following function. But it didn't work. ...
0
votes
2answers
106 views

Create my own `PrimeQ` function [closed]

I want to create my own functions, for example: Functions like IntegerQ,EvenQ and OddQ. My ...
0
votes
0answers
42 views

How to use === with condition?

I have two expressions, and they are same when k is positive and x is non-zero real number. Below code gives me ...
0
votes
0answers
23 views

Why doesn't Head[expression] == Real serve as a test for expression being Real? [duplicate]

Although Head[expression] == Real seems to return True whenever expression is a Real, it does not return ...
0
votes
0answers
40 views

How to test consistency of two assertions without hacking

Suppose I have a set of assumptions assum = x ∈ Reals && y ∈ Reals and I want to test an assertion like ...
0
votes
1answer
78 views

TrueQ returns False [closed]

I have coefficient of some expansion: Workingexpansion = tau/n - (A tau^2)/(27 n^3) - (B tau^3)/(5832 n^5); CoefficientList[Workingexpansion, tau][[2]] ...
0
votes
1answer
85 views

Trying to generate random even number

I am trying to generate a random even number, and then try to write the list of primes that are composing it as Goldbach conjecture says. It's just a test to learn how to use mathematica, so I would ...
5
votes
0answers
56 views

Testing for membership with Bags?

Is there a faster way to test for membership in an Internal`Bag other than unpacking the whole thing like this? ...
2
votes
2answers
81 views

How to tell whether a character is a letter-like form

Is there any way to programmatically tell whether a given character is a letter or letter-like form (see this reference page for what I mean)? One idea I had was to use ...
20
votes
2answers
3k views

Determine whether some expression contains a given symbol

Given a symbol t and an expression expr, how can I determine whether or not the symbol t ...
0
votes
0answers
52 views

How to check if all the entries in columns of a matrix are equal?

Assume we have the following matrix/tensor. How can I test if the column has the same element? 4-6 and 8-9 columns has the same element. $ \left( \begin{array}{cccccccccc} \{2,3\} & \{2,3\} &...
1
vote
2answers
52 views
0
votes
1answer
68 views

If ValueQ is buggy, what alternative is there?

The function ValueQ has been irritating me for a while. I can't find its use for anything. Inspect the following: ...
4
votes
2answers
252 views

How does RootOfUnityQ work?

How does Mathematica's RootOfUnityQ function work? That is, how does Mathematica know if a number is a root of unity? Example: Let $x = \frac{1-i \sqrt{2+\sqrt{5}}}{1+i \sqrt{2+\sqrt{5}}}$. Then <...
1
vote
1answer
315 views

problem with testing if two expressions are equal

I have a small problem: I have two expressions: a = (ia*l^3*p0)/(12*ia*l + 6*i*la) b = p0*l^2/(12*(1 + 0.5*i/ia*la/l)) Obviously, they are equal. Just take ...
14
votes
2answers
956 views

Checking if a word exists

Probably the simplest way to check a word if it exists is to use DictionaryWordQ[] DictionaryWordQ["color"] True But it ...
8
votes
2answers
451 views

Using OddQ and EvenQ in piecewise functions: Buggy?

I was trying to evaluate a sum over a piecewise function, not unlike this example. However, my piecewise function needed to be defined differently for even and odd ...
1
vote
0answers
106 views

Want to know more about _?MatrixQ [closed]

User, @AndrzejKozlowski has uploaded a number of interesting demonstrations to the Wolfram Demonstration Project. I have a particular interest these days in his Pricing a Bermudan Option with the ...
4
votes
2answers
100 views

Condition syntax: “when equal to any of”

I am trying to write a condition clause for a certain expression. I need to pick out the following cases: Mod[x*y, 10] == 8, or Mod[x*y, 10] == 3, or Mod[x*y, 10] == 7. I need to repeat ...
3
votes
1answer
134 views

How to remove symmetries from this list?

First of all, I work with modular arithmetics and the elements of the arithmetics are lists themselves. I recognize two kinds of symmetries - shift and mirroring. We could define shift of a list like ...
1
vote
0answers
52 views

Speed up for SequencePredictorFunction?

From Google Dive: SequencePredictorFunction is here, along with my test data. From pastbin: prediction function and data is here. Using the ...
9
votes
1answer
187 views

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

The command SameQ[1, Null] returns False which is what I would expect, but the command ...
10
votes
5answers
745 views

Test if a list is a constant integer multiple of another list

I have a list of lists, and I want to eliminate all the lists that are constant integer multiples of another list. My initial approach was to divide the lists using nested tables. ...
6
votes
2answers
394 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: ...
5
votes
1answer
115 views

PrimitiveMatrixQ?

Is there a simple way to test in Mathematica whether a non-negative square matrix $A$ is primitive? Primitive means that for some positive integer power $k$, all entries of $A^k$ (matrix power) are ...
2
votes
1answer
53 views

compare some functions

Assume that I have three function: sum1[n_] := Sum[Cos[k/n], {k, 0, n}] sum2[n_] := Sum[Sin[k/n], {k, 0, 2n}] sum3[n_] := Sum[Cos[k + 1/2n], {k, 0, 2n - 1}] For ...
18
votes
3answers
3k views

Checking if a point is in a convex 3D polyhedron

Extending from these questions How to check if a 3D point is in a planar polygon? and How to check if a 2D point is in a polygon?. I'm trying to do this to render specific shapes made up of spheres. ...
1
vote
2answers
49 views
1
vote
1answer
123 views

Simplify nested If into a loop

I would like to simplify a set of tests (meant to be applied on a random set of parameters), written for now as nested If: ...
6
votes
1answer
86 views

TagSet for symbol inside NumericQ behaves differently than in other fooQ functions

I am trying to define some symbols as being numeric by using TagSet and encountered the following different behaviors between NumericQ and e.g. ...
0
votes
1answer
150 views

A basic question about Equal [closed]

Can someone explain me why the following evaluates to True? Pi/2 == Pi/2. (*True*)