Questions about how Mathematica evaluates expressions, tracing evaluation (Trace*), handling expressions in unevaluated form (Hold*, Unevaluated), nonstandard evaluation, etc.

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1
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1answer
62 views

Trace and SameTest in Union [closed]

This question is actually two question. First, I feel so stupid that I just don't understand the use of theSameTest option in ...
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1answer
41 views

How to enable automatic “grammar check” for MMA? [duplicate]

The special evaluation mechanism of MMA might make it more likely for MMA users (especially new users) to make mistakes and more difficult to find them. For example, one may have defined a function ...
5
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2answers
240 views

Evaluate notebook from other notebook

I have a notebook ("notebook 1") which in the beginning sets some parameters, does something depending on their value and saves the result to a file, say: ...
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1answer
132 views

Why isn't Mathematica reducing my result to a number? [closed]

I do not understad why the program do not show the number values. Even when I use N[xx]. How can I simplify this?
5
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3answers
74 views

StepMonitor won't display Plot

This example is from the documentation under Monitor ...
0
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0answers
42 views

Evalutation strategy [duplicate]

This example code: ...
16
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3answers
279 views

Is it possible to change the order that symbol definitions are checked? (DownValues vs UpValues)

Suppose I have the function f with the following definition assigned to it: ...
4
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0answers
90 views

Simple arithmetic with Irrationals fails [closed]

While solving a simple puzzle that asked for a few calculations in plane geometry, I ended up with this expression: $-\frac{55}{2}+\frac{\sqrt{27233}}{2}+\frac{1}{2}(55-\sqrt{27233})$ Or, in ...
2
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2answers
79 views

Singleton pattern

How can I implement the singleton pattern in Mathematica in order to ensure that a symbol is not redefined if it's already defined ? This can be useful for example with global variables in packages ...
4
votes
1answer
363 views

mathematica does not evaluate without internet access? [closed]

I am watching the video Hands-on Start to Mathematica Basic Graphics and for about 15 minutes I was trying to evaluate $\frac{\sin x}{x}$ and each time I encountered errors like: The result can ...
17
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2answers
313 views
3
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1answer
61 views

How to evaluate an expression via `LinkWrite` when the expression is only known at runtime?

*** Here's the original post... I'm setting up a secondary kernel in sandbox mode with LinkLaunch, and need to pass various expressions to it for evaluation. These ...
1
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1answer
98 views

Evaluate multiple notebooks sequentially and automatically

I know how to run multiple notebooks at once. But my problem is that due to the RAM capacity, I have to run these notebooks consecutively. Another problem is that since I may not be in my office all ...
7
votes
1answer
139 views

How would one return from a place of a pure function's body using Return?

From previous answers, replies and discussions it is known, while not formally documented (even in the most recent Wolfram Language Documentation Center), that Return can be used in a two-argument ...
0
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1answer
90 views

Special fractions generator

Note that 13/33, 1313 / 3333 , 131313 / 333333, ... They are always equivalent fractions Fraciones generate desire to have this property based arbitrary ...
5
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1answer
35 views

How could I set TimeConstrained globally?

I want to set TimeConstrained globally, I tried use $PrePrint as bellowed script: ...
1
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3answers
101 views

Keep leading/trailing zeroes (like Defer except with numbers) in a given number

I'm trying to write a function that counts the number of significant figures a given number has so I can ensure my calculations are rounded correctly; however, I am having a lot of trouble preventing ...
1
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1answer
48 views

problem about Root and Hypergeometric2F1

See these example, why does the output is different? ...
10
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2answers
435 views

A problem about the implementation of Bezier curve

I implemented the Bezier curve like built-in BezierCurve as follow: SplineDegree -> d specifies that the underlying ...
1
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1answer
55 views

How to achieve fun[Unevaluated[f][Unevaluated[x], Unevaluated[y]] in a more elegant way?

I have defined a function fun[f_[x_,y_]]. When I call it, I want to wrap everything by Unevaluated: ...
-2
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1answer
81 views

Why is my function returning 0 when when I try to give it arguments by replacement? [closed]

I tried running a function f with rules and calling it directly with arguments specified directly but the one with rules returns zero while the one with direct ...
6
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2answers
113 views

Force evaluation of the right-hand side of a local variable definition

One can do expression = a + 1; f[a_] := Evaluate[expression] but how would one do something like this ...
3
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2answers
148 views

Even with Evaluate[], Mathematica is plotting everything in the same color

The code evals[x_?NumericQ] := Eigenvalues[{{x^2, 2 x}, {x, 3 x^2}}]; Plot[Evaluate[evals[x]], {x, -1, 1}] gives both eigenvalues in the same color. I thought ...
7
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2answers
109 views

Cannot Block Plus

It is customary to use the following idiom to partially evaluate something inside a held expression: ...
4
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1answer
129 views
7
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2answers
139 views

Inserting symbols' definitions during read time of the code

Let's say we've got a package: ...
1
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5answers
170 views

Do not expand matrices in Mathematica calculation

Here is an example of a problem I'm having. Consider that I have defined: omega={{p[t]},{q[t]},{r[t]}} x={{a},{b},{c}} R={{1,2,3},{4,5,6},{7,8,d}} What I would ...
5
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2answers
132 views

A pre-parsed HoldForm

HoldForm holds an expression's parsed form not its actual "inputted form" e.g. ...
6
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2answers
257 views

How do I “evaluate in place” programmatically? Need to evaluate Defer[] result in non-interactive setting

I need to evaluate the result returned from an external package, which contains Defer in it, but do this in a script without user interaction. I am not able to ...
7
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1answer
130 views

Unevaluated @ {args} versus Unevaluated /@ {args}

Working my way through Robby Villegas's lovely notes on withholding evaluation, I almost got Polish Notation on my first try. Here is my final solution, which seems to work well enough: ...
4
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5answers
164 views

Using Through with SlotSequence

I have an expression consisting of a few pure functions added together like so: f+g+h I want to add the bodies of these functions together and make that a pure ...
3
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1answer
62 views

SelectionEvaluate executes out of turn

I'm seeing some unexpected (to me) behavior from SelectionEvaluate. I've got a notebook with two sections. In section 2, I've got code that clears the notebook's ...
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0answers
19 views

Manipulate inside Module - “Order of evaluation conflicts” [duplicate]

In this example, Manipulate is contained within a Module: ...
2
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1answer
70 views

Non-autonomous Dynamical system Sliding mode controller Error

This code is a simulation of a sliding mode controller of a non-autonomous dynamic. When I use ArcTan in input, I receive an error. ...
4
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2answers
131 views

Simplifying expression with non-commutating entries

Say I have an expression such as (a + X)**(b-Y) where the variables above possess the following commutation relations [a, b] = [a, X] = [a, Y] = [b, X] = [b, Y] ...
3
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0answers
54 views

Why does FreeQ seem not to work with complex numbers?

I guess I do not understand how Mathematica evaluates this simple expression inside FreeQ ...
3
votes
2answers
178 views

Optimize evaluation time for a Quantum Walk simulation

Here's the problem. I'm trying to simulate a noisy Quantum Walk to obtain results similar to these, experimentally obtained. I wrote my code, and I get results which are in accordance to what I ...
7
votes
1answer
272 views

NMinimize with NIntegrate (crash in symbolic evaluation, memory leak)

This is a "common" problem from what I've seen, but with a different spin. I have a function I use often that finds a fit of an expression to another expression with some free parameters (e.g. for ...
4
votes
1answer
68 views

How to define an expression which is differently evaluated in calculations and printed

Let's say, we have a list: values = {1.2, 0.04, 0.9}; Is it possible to replace 0.04 by some expression, which displays as ...
1
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3answers
64 views

Controlling the evaluation of other arguments in pure functions [duplicate]

I have a piece of code where I would like to do the something like the following: ...
2
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2answers
156 views

Why does Mathematica not evaluate the difference recurrence using `RSolve` or `RecurrenceTable`?

Mathematica does not evaluate the following recurrence of two variables using RSolve and only echoes the input: ...
4
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1answer
101 views

Formal Differentiation

I'm trying to formally differentiate an expression. (I am aware of how to differentiate formally?, but am unable to generalize the idea) For example: ...
6
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3answers
140 views

Evaluate a expression split in a list

I have a list with this format {integer, sign, integer, sign, integer}, sign being one of these: Plus, Subtract, Times, Divide. For example, let's say: ...
8
votes
1answer
209 views

Trouble with polynomial multiplication

Bug introduced in 10.1.0 and fixed in 10.4.0 ...
2
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2answers
153 views

How can I partially evaluate a function?

I have a multivariable function, from which I'd like to define a marginalization: f(a,b,c,d,...,z) ---> g(a,1,c,d,...,z) Generally, g will have fewer argument than f, possibly none (full ...
1
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0answers
108 views

How to Implement a “Function Object” suitable for NDSolve and Finite Element Method?

I have a bunch of methods that shoud return an expression that behave like a function, i.e. an expression that, when supplied with suitable arguments, evaluate to something. A simple ...
2
votes
3answers
57 views

Display a part of a notebook when MMA has done evaluating it

When you evaluate a notebook, it begins to slide upward and shows you a different part of your code, several cells upstream of the notebook... I was wondering if there is a command that could always ...
9
votes
1answer
179 views

Comparing exact expressions for equality — is it really OK if I get wrong answer?

Bug introduced in 7.0 or earlier and fixed in 10.2.0 I found an unexpected behavior (that I think of as a bug) in evaluation of the equality operator applied to mathematical functions with exact ...
2
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1answer
80 views

Failure in the use of FullSimplify

My question is about an apparent failure of the function "FullSimplify" to simplify an easy algebraic expression. This is the expression that I ask Mathematica to evaluate: ...
3
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3answers
106 views

How to force evaluation on the right of an @ operator?

Is there a way to force evaluation on the right before the Prefix operator (@) without using parentheses? I came across this question when I was working with the ...