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

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4
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103 views

Why the flat f[x] is treated as ghostHead_[f[x]]?

While reading this answer I feel confused. If we do not care any specific detail of the original question, then ybeltukov's answer essentially makes use of the following fact ...
4
votes
0answers
145 views

Can I define an axiomatic (Boolean algebra) system and prove theorems using Mathematica?

The general question is Can I define an axiomatic system and prove theorems using Mathematica? The more concrete one is about Boolean algebra. I consider this axiomatic Boolean algebra system ...
4
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0answers
62 views

Regarding Evaluated True

Done a bit of reading: Normal[Series[ ]] does not give a normal expression Regarding the Evaluated->True, consider: ...
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0answers
39 views

Use EvaluationCompletionAction to notify me only after long evaluation

Is it possible to use the option EvaluationCompletionAction to notify me (e.g. with a Beep[]) when an evaluation that took ...
4
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0answers
189 views

DynamicModule, SaveDefinitions and global functions

Unfortunately, I had not checked stackoverflow, because there, the exact same behavior was already reported. Please see the Q&A "SaveDefinitions considered dangerous". Up-front, I'm on Ubuntu ...
4
votes
1answer
209 views

Manipulate a Plot that contains a variable that contains symbol [duplicate]

This snippet mm = m Manipulate[{mm, Plot[mm x, {x, 0, 1}]}, {m, 0, 1}] (m is not defined anywhere) produces a sadly fixed ...
4
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0answers
77 views

Problem with inequality using refine

I am using inequalities to follow some line of reasoning in Mathematica and I came across a problem I can not explain to myself. Does from a>=0 and b>=0 not follow a+b >= 0? How does Mathematica ...
3
votes
3answers
531 views

Help on evaluation control?

I want to plot series of slopes: x, 2x, 3x, 4x, 5x, 6x... I'm trying to do this: ...
3
votes
2answers
293 views

Efficiently evaluating a held expression directly from a list

I am able to evaluate a held expression that I have put on a list by: ReleaseHold[expressionList[[1]]] and ...
3
votes
1answer
188 views

Evaluation order of Button[]'s action

it looks like it should be well known issue but I haven't found answer anywhere. Please tell me why the result (after clicking) of this: ...
3
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3answers
128 views

UpValues evaluation with Dot operator

I would like to simplify some database notation, and I'm doing some tests with UpValues for that. For example, if I set this Upvalue fot tab1: ...
3
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3answers
130 views

Using a variable to tell Mathematica which existing variable to manipulate

I have an estimation routine I have coded up, I want now to do some tests on it where I pick a particular parameter and run the estimation for differing values of that parameter. What I want is to be ...
3
votes
3answers
174 views

HoldForm: how does it interact with nested evaluations?

Here's an example to illustrate the issue I'm having. right = 8 - y; left = y^2 + 6; integrand = HoldForm[Evaluate[right]] - HoldForm[Evaluate[left]] (I ...
3
votes
3answers
215 views

Alternative to using global variables in functions?

Often times I find myself using unevaluated variables (i.e. they show up blue) as dummy variables in whatever I'm returning such that I can evaluate them as needed later on. A simple example is as ...
3
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1answer
295 views

Log function - why is Log[b,b] not being evaluated to 1?

Have been experimenting with the Log function to demonstrate simple Log relationships such as Log[xy], Log[x+y] etc. ...
3
votes
2answers
294 views

How to NOT simplify fraction

How can I prevent Mathematica from simplifying fractions? What I would like to do is run a test on a list of fractions to see how many are in their reduced form. For example, I have a list: ...
3
votes
5answers
179 views

Algebraic expressions on pure functions

I would like to know how to perform algebraic operations with pure functions. Simple version: Here's a silly toy model: I want to transform the algebraic expression Sin*Cos into the function ...
3
votes
2answers
115 views

Turning evaluation off

I am making a directed graph, but Mathematica keeps trying to evaluate my labels. I know that I can just use " ", but I have a lot of input. Is there a way to turn evaluation off? ...
3
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1answer
152 views

Set promotes Rule to RuleDelayed?

In mentally building a model of how Mathematica works, I naively expected Set to create a Rule in a symbol's ...
3
votes
1answer
141 views

Output an Expression in terms of GoldenRatio

Sorry if this is a dumb question (I'm new). I swear I searched and read forums first! I'm trying to rewrite expressions in terms of the Golden Ratio. For example, I know 9+4Sqrt[5] is Phi^6, but can ...
3
votes
2answers
105 views

Side-effecting an array in an association?

I'm working on some classical data structures (stack, queue, etc.) and want to mimic oo style in MMA. As a first attempt, I want to store an array in an Association, like this: ...
3
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2answers
189 views

How to define the irrational domain or any other arbitrary domain?

I have found no way to define the domain of Irrational numbers. I can easily define a test to see if a number is irrational by defining: ...
3
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1answer
75 views

Evaluation of Derivative in a Module

Can someone help me understand the evaluation procedure in the following two pieces of code? ...
3
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2answers
45 views

Evaluation control with TagSet

Suppose I have a property associated with two functions using TagSet: ...
3
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3answers
117 views

ReplacePart equivalent for Associations

I have a fairly complicated Association. I wish to use/create a function such as ReplacePart to operate on certain Keys within this multi-level Association. Here's ...
3
votes
2answers
164 views

Assigning an equation as a variable

I am compiling a calculator where many slider parameters are used to define a value, where the defined value may then be reused to define another value. I am unable able to, or at least been ...
3
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1answer
316 views

Why can't Mathematica parallelize this?

The following code makes mathematica print "ParallelTable::nopar1: [...] cannot be parallelized; proceeding with sequential evaluation." ...
3
votes
1answer
502 views

Is there anything like a C pointer (or returning a reference) in $Mathematica$?

I want to do in Mathematica what the following does in C. ...
3
votes
1answer
302 views

Gateaux (directional) derivatives and higher order differentials of a functional

I would like to calculate the Gateaux derivative of a functional (i.e. a function depending on functions). A simple example for the Dirichlet functional: $L(u(x))=\int_0^1 \frac{1}{2} (u'(x))^2 dx$ ...
3
votes
1answer
91 views

How to localize symbols on the right-hand side of Rule when using ReplaceAll?

I am frustrated by the following: {1, 2, 3.0} /. a_Integer -> a + 1 The a on the left side of the arrow is localized and ...
3
votes
2answers
160 views

Stopping a head from evaluating more than once

While attempting to answer my own question, Is there a way to "hold" prefix / infix / postfix notation?, I came across the need to evaluate a recursive function only one level deep. For ...
3
votes
2answers
150 views

Bare symbol invocation fails but not if used with an argument

How to achieve the following behavior on a symbol f? Background: The main goal is to use the symbol to tag an abstract data structure where downvalues are used to store information. Only defined ...
3
votes
2answers
80 views

Confused with HoldForm in Postfix notation

Why does the following code produce different result? In my mental model, they should be the same. ...
3
votes
1answer
109 views

Why is held expression evaluated?

Context: I'm studying non-linear dynamics. As part of a bigger problem, I'd like to generate lists of the form {{deq, ic1}, {deq, ic2}, ...}, where ...
3
votes
1answer
630 views

How can I save the current evaluation state of a notebook and start from it later?

I currently have a nested Table command running (in Mathematica 9), with two progress bars to track the variables. I have to shut down or hibernate the computer in ...
3
votes
1answer
108 views

Stop TradtionalForm evaluating expression

I'm trying to get this expression to display as typed instead of evaluating the 1/1.121. ...
3
votes
1answer
67 views

Why doesn't my expression evaluate at the subkernel?

Consider this code: ...
3
votes
1answer
74 views

Defining a function that prints both the name and value of a variable defined locally within the calling function

To save time when debugging with Print statements, I'd like to define a function -- call it PrintVal -- that prints both the name and value of a variable defined locally within the calling function. ...
3
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1answer
68 views

Print prints into the Messages notebook rather than into the evaluation notebook

Some time ago I noticed that the results of the evaluating the function Print[something] does not emerge in a new cell created in the notebook where the operation ...
3
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1answer
61 views

Apply a function to the current selection in place

Say a have the function foo: foo[x_] := x + 2 Like the Evalution ...
3
votes
1answer
83 views

Where do Mathematica's probability functions draw a line in the sand for predicates?

Thinking about a recent question mis-posted here (belonged on math), I noted the following. A contrived example - probability that a or b are 1: ...
3
votes
1answer
103 views

How to calculate the residue of $1/f(z)$ at a numerical approximation to a root of $f(z)$?

The input Residue[1/DirichletL[19,10,s],{s,s0}] gives 0 even when s0 is a root. For ...
3
votes
2answers
141 views

Evaluate in Plot leads to function error

Please help - I'm really struggling to understand why this evaluates with errors. ...
3
votes
1answer
413 views

Use output of NDSolve as an integration limit of NIntegrate

I've been working on a ODE, for a function y[t], that, due to it's complexity, has to be solved numerically. I then need to use the results of NDSolve, which I ...
3
votes
2answers
293 views

Overloading conjugate operator for a particular function

I trying to modify the behaviour of the built-in Conjugate[] operator on a particular function I have defined, to take into account that some of its variables are ...
3
votes
1answer
283 views

FunctionInterpolation Errors / Question re Evaluation Order and Options

I have using Mathematica functions that takes a Cartesian coordinate relative to the Earth (xyz) and converts it to a latitude, longitude, and altitude (lla). And here it is: ...
3
votes
1answer
58 views

A problem about sorting final result

Three days ago, I asked a question about B-Spline Basis fuction here @Michael E2 given a solution to make the order of interval looks normal The easiest way would be to sort it afterwards: ...
3
votes
1answer
136 views

Why even try the semantic constraints, if expression can't match the pattern structure?

This result is unexpected: Trace[MatchQ[{7}, {_?NumberQ, __}], NumberQ] (* -> {{NumberQ[7], True}} *) Why evaluate ...
3
votes
2answers
124 views

Keep data in memory inside a notebook without having to evaluate it again [duplicate]

I have a notebook that calculates some data in a relatively large time so I want to keep these data saved inside the notebook without recalculate them every time I open the notebook. I know I can ...