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

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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
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0answers
90 views

Functional-Style Fixed-Length Queue Object?

Following up on question Side-effecting an array in an association? and @Mr.Wizard's answer in there, I'm modernizing and tweaking Daniel Lichtblau's efficient queues and ran into a little roadblock. ...
3
votes
0answers
173 views

Memory problem in Mathematica 10

I'm having a problem with memory. I'm doing nonliner fits of several data lists to a system of differential equations. When I evaluate the "Do" cycle the memory grows with the iteration step up to my ...
3
votes
0answers
114 views

Assign variables from list inside With or Module

I have found that it is possible to assign variables from lists, as follows. r = {1, 2, 3}; {a, b, c} = r; b 2 However, ...
3
votes
0answers
71 views

Non-preemptive evaluation of a dynamic function? [duplicate]

I want to monitor a long calculation that is triggered by the release of a Slider. While one can indicate running calculations when the main evaluation loop is ...
2
votes
2answers
384 views

Get the approximate analytical solution to an algebra equation

Is there a way to get the analytical form to the root of this equation: 2 A e (-ArcTanh[smax/s0] + ArcTanh[(smax Cos[w ζ])/s0]) == F0 ...
2
votes
2answers
146 views

How to make Mathematica returns the exact expression I typed

I'm using Mathematica to compare some constants. Before playing around with those constants, I would like to check that I didn't make any mistake in typing them. So my question is the following: "What ...
2
votes
3answers
115 views

Evaluation inside a Manipulate

Let's assume I have a symbolic expression, and inside a Manipulate I define the actual values: ...
2
votes
2answers
151 views

Time delayed evaluation of a function

I'd like to write a function that delays the evaluation of a function (say) $5$ seconds after I hit Shift+Return. Is this possible?
2
votes
1answer
249 views

Nested Derivative

These two expressions are mathematically the same, but when substituting with the same rule, yield different results. What is happening? ...
2
votes
3answers
604 views

Select sublists with second element nearest to zero

I've got some big lists from which i need some data (one of the big lists). To be specific, I need to divide this biglists in sublists of the same length (10000), and form a new list with the mean of ...
2
votes
3answers
6k views

Step-by-step definite integration

I am interested in obtaining the intermediate steps for rather straightforward symbolic definite integrations (e.g., from an elementary calculus text). As an example, for $\int_0^1 x\,dx$ I'd like ...
2
votes
3answers
168 views

Dynamic plot with Evaluate on expression

I'm trying to make a make a plot of a table of expressions, which should be pre-evaluated (since they are infinite series with analytic sums). I'm able to make the plot normally with ...
2
votes
2answers
65 views

Get the unevaluated expression from a numbered cell

If a cell exists as below: In[1] := (xyPoints = {{1,2},{2,5},{3,10}}; ListLinePlot[xyPoints]) Is it possible to get at the expression rather than the plot shown ...
2
votes
3answers
113 views

Strong glitch with Evaluate in Manipulate

I'm experiencing a strong evaluation problem for a Manipulate box and I can't find the best solution yet. Here's a MWE to show the glitch : ...
2
votes
2answers
86 views

PasteButton: Pasting expression name without quotation marks?

I am struggling to find a way to use PasteButton to paste the name of an expression (in particular a list) without showing the contents of the expression or without ...
2
votes
1answer
88 views

Block assignments not quite sequential?

With scalars, Block acts like Scheme's let*, that is, the assignments (appear to) happen sequentially: ...
2
votes
1answer
76 views

Show [In] and [Out] tags after quitting Mathematica

I cannot find a way to show [in] and [out] tags when evaluating cells after I close the application. Is there a way to keep these shown? I disabled the kernel in global options but cannot transfer ...
2
votes
2answers
71 views

function definition with a given list of parameters: how to use Evaluate[] properly?

given a list of variables variables = {a, b, c}; I want to automatically define a function f[{a_,b_,c_},x_] := g[a,b,c,x] ...
2
votes
2answers
135 views

Handling a sequence of unevaluated arguments

I have the following piece of code: ...
2
votes
1answer
268 views

Is there a way to simplify a symbolic expression at assignment, once-for-all?

I have a series of symbolic function calls that could be greatly simplified using some assumptions. I think I would like for these assumptions to be used in the definition of the function so that they ...
2
votes
2answers
126 views

Merging two held expressions into a held compound expression

Consider e1 = Hold[a = x + x; b = y + y + y]; e2 = Hold[c = a + a + b + b + b; c^2]; How can I obtain the following? ...
2
votes
1answer
124 views

Strange results of definitions using OwnValues

I am asking this question simultatenously with this one, which is strongly related. I was trying to see if I could create the behaviour as in that question without using ...
2
votes
2answers
333 views

While loop doing cell evaluation not completing

I am trying to get a loop structure using While to repeatedly evaluate another cell referred to in its body (using a cell tag). ...
2
votes
2answers
346 views

Evaluating Polynomials at Grid Points

I am continuing my quest on B-splines. The code below builds a 5x5 matrix out of B-splines, using the BSplineBasis[] routine. I now want to evaluate the polynomials that are stored in each matrix ...
2
votes
2answers
177 views

Updating a tracked symbol inside Refresh?

I have some code inside a Manipulate, whose goal is to allow the user to edit the upper half of the matrix while keeping it symmetric at all time. The minimal code ...
2
votes
2answers
2k views

Animation of Differential Equations from NDSolve with ParametricPlot3D and Evaluate

I have a system of differential equations (referred to as "s") and use NDSolve to obtain the solution. I substitute the interpolated functions for the original ...
2
votes
1answer
973 views

A combination of Set::setraw and Set::shape errors

Please consider the following toy code: ...
2
votes
1answer
84 views

Errors in plotting regular function

Suppose we want to define Tanh-function via exponent: th[x_] := (1 - Exp[-2 x])/(1 + Exp[-2 x]); FullSimplify[th[x]] Out[13]= Tanh[x] Then we define new ...
2
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2answers
80 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 ...
2
votes
2answers
81 views

Evaluation speed of apparently equivalent functions

Consider the following expressions: f[x_Integer] := x, f[x_] := x /; x ∈ Integers, f[x_?IntegerQ] := x All of the expressions above (and probably others which ...
2
votes
1answer
88 views

Return the incomming expression on false

when I have an expression, that is unknown to mathematica, it is returned exactly the same, as it was called. For example SeeFlyingPigs[1,2] called on the line ...
2
votes
1answer
83 views

Need to run evaluation 2 times

Why does this only work after running the evaluation 2 times? ...
2
votes
1answer
263 views

Expectation function does evaluate my expression

I am trying to evaluate the expression Expectation[(B x (-6 b + 12 a n0 + B x + B^2 x^2))/(2 (6 a + B x + B^2 x^2)), Distributed[x, BetaDistribution[α, β]]] ...
2
votes
1answer
449 views

Working with derivative of conjugate of a complex number

I have a complex function, lets say $g(x)$. I want to take its and its conjugate's derivative. I need the solution of derivative which must be symbolically and computationally efficient. Lets take an ...
2
votes
1answer
143 views

Mathematica displays the unevaluated expression Expectation function

The evaluation runs for a few seconds and then Mathematica displays the unevaluated expression Expectation function ...
2
votes
2answers
129 views

Pattern matching to head with HoldFirst

I want to define a function that only operates on expressions with a head from a given list, such as f[expr:(_And|_Or)] := Print["LHS is ", expr[[1]]]; This of ...
2
votes
1answer
103 views

Defer parts of the expression

Is there a way to Defer only parts of the expression? For example, I have a=1; and then I want the expression to be shown as...
2
votes
1answer
209 views

Wrapping at evaluation for inline cell

I've been playing with inline evaluation and I've came to the conclusion that it's most convenient to put the Dynamic@ inside the inline cell, so I've started to ...
2
votes
2answers
84 views

Can I have Mathematica show intermediate forms before final evaluation?

If I have x = 2 and I want to evaluate y = x^2 I would like to the output to show ...
2
votes
1answer
114 views

Manual CellGrouping option causes crash at cell evaluation

Update: Try to reproduce this behaviour with CellGrouping set to manual. To do that: either evaluate ...
2
votes
1answer
302 views

Why is this expression being held, and how can I evaluate it?

I can't figure out why an expression isn't evaluating, even though there's no Hold* in its FullForm: ...
2
votes
1answer
438 views

Evaluate Numerator and Denominator Separately

I have this function. ...
2
votes
3answers
160 views

Function to preserve evaluation on display?

I'm looking for a function that applies the following behavior to an expression: -When the expression is given as the full input, or as part of a function that cannot be evaluated, it remains in ...
2
votes
1answer
52 views

recursively structuring a multivariate numerical optimization

Suppose that I want to partition the unit interval [0..1] into four subintervals whose max length is as short as possible. I can ask Mathematica to: ...
2
votes
2answers
162 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: ...
2
votes
2answers
157 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 ...
2
votes
2answers
168 views

How to apply list of values to a list of functions

I have the following: first= {1+a,2+a,3+a,4+a} and a list t={0,1,2,3} I want to evaluate the first element of "first" at ...
2
votes
1answer
65 views

Is there a simple function identify the sign of an expression given constraints

I'm looking to find a simple function that can identify the sign of an expression given a set of constraints. I have looked around and do see that there is a few threads on this but I'm not sure I ...