# Questions tagged [expression-test]

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### How to check if a 2D point is in a polygon?

Background: I use code from An Efficient Test For A Point To Be In A Convex Polygon Wolfram Demonstration to check if a point ( mouse pointer ) is in a ( convex ) polygon. Clearly this code fails for ...
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### 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: ...
716 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 ...
3k 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 ...
3k 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 <...
369 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 ...
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.
9k 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 ...
441 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 ...
1k 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 ...
225 views

### IsomorphicGraphQ fails to recognize that two empty graphs are identical

Bug introduced in 9.0.1 or earlier and fixed in 11.0.1 Consider the following two graphs: ...
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### How do I get Mathematica to return a function call unevaluated?

How do I get Mathematica to return a function call (conditionally) unevaluated? I expect this may use the slightly-mysterious Hold function. As a toy example, ...
465 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 ...
593 views

### TrueQ returning False on true statement

Why does TrueQ return False on the following? TrueQ[Log/Log == 1/3] (* False *) ...
572 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 ...
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. ...
975 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 ...
230 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. ...
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 ...
15k views

### How to detect if a sequence of integers is consecutive

I'm not a math-guy really (a programmer actually) and this is my first question. And excuse me if I can not explain my problem good. The problem is I have a sequence of integers and I want to detect ...
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### 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. ...
264 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 ...
172 views

### Can anyone guess what InternalRadicalMemberQ does?

There is an undocumented function InternalRadicalMemberQ which takes two arguments. But whatever input I try for the two arguments, it seems to crash the kernel (...
222 views

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

Bug introduced in 10.0.0 and fixed in 10.1.0. While answering Pattern match for nested Association I came across behavior of MemberQ and ...
857 views

### Checking if all the variables are present in the defined function

I want to check if a user input the function with all the specified variables or not. For that I choose the replace variables with some values and check for if the result is a number or not via a ...
374 views

### Picking points in a plane under a curve given by a list

Suppose that I have a set of points in a plane, which range from $x\in [0,20]$ and $y\in[0,10]$, and a curve given by a list of points in the same region: ...
580 views

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

The documentation for PossibleZeroQ says: With the setting Method->"ExactAlgebraics"...
403 views

### Understanding SameQ

I am new to Mathematica. So I have read the documentation for comparing expressions in Mathematica and I still don't get the SameQ (===) function. Let me give you a short example: ...
452 views

### Why is an empty list not tested by VectorQ?

I am a bit amazed by this behavior of VectorQ[ expr, test ]: VectorQ[ {}, NumberQ ] True It seems that the test itself is ...
592 views

### Difficulty understanding difference between == and ===

After doing this: ...
208 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 ...
105 views

### Are UnsamQ and Not[SameQ] the same function? [closed]

Why are the following functions a[x___] := If[ UnsameQ[x, Null], 1, 2, 3] b[x___] := If[ Not[SameQ[x, Null]], 1, 2, 3] different? For example ...
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### 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 <...
220 views

### ValueQ returns false positive for one argument type only

I'm seeing some perplexing behavior from ValueQ in 10.3. Consider: ...
193 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 ...
142 views

### Mystery with ValueQ

Consider the following ClearAll[jd]; ValueQ[jd] We expect False and get it. Now consider ...
173 views

### How to test if a GeoPosition is inside a geographic Polygon?

I have tried the following: ...
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### Difference between != and =!=

I (think I) understand the difference between == (semantic) and === (syntactic). So when comparing != and =!= I was expecting a similar difference. So can anyone explain why the third line in this ...
508 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 ...
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### Can I make IsomorphicGraphQ consider other properties besides the EdgeRules?

Consider two graphs, which are isomorphic to each other based on the vertices and edges, ...
184 views

### Can I make NumericQ Listable? Why isn't there an Option to test in ListQ?

I have a function which takes lists as arguments. But it shall be evaluated only, if the elements in the lists are all numeric. Otherwise I want the function to remain unevaluated. There is a ...
442 views

### Sum with IntegerQ does not converge

Why does Mathematica return: Sum::div: Sum does not converge. >> when I input: ...