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

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16
votes
4answers
452 views

Prevent graphics render inside held expression

Assuming each odd line is input I would like the even lines to be the output of the following lines. In the above the Graphics are inside ...
2
votes
1answer
95 views

How can I set a RadioButton to invoke an action, like a Button can?

In Mathematica one can create a Button which, when clicked, invokes an action. For example... ...
9
votes
1answer
157 views

Tracking Initialization

How to track Initialization step by step? Any tricky solution is ok. One condition, x should be ...
16
votes
4answers
686 views

HoldForm doesn't hold form

Bug introduced in 10.0.0 and fixed in 10.0.1 In Mathematica version 10, HoldForm no longer produces the same results as in version 8 (edit: I only have versions ...
5
votes
2answers
165 views

Strange Behavior when making Equal Listable in Pick

While trying to make this problem more efficient I tried different methods and dabbled with making Greater and Equal ...
6
votes
2answers
138 views

Showing “updating…” message while Manipulate is re-evaluating

Is it possible to show a fixed text such as "updating..." instead of the last result shown, when Manipulate is re-evaluating an expression (in a slow evaluation ...
11
votes
2answers
325 views

Return partial result when MemoryConstrained aborts NDSolve

I use NDSolve to solve a large set (~400) of coupled ODEs. Sometimes, the memory (~4GB) gets filled up, and my computer becomes impossible to work with, because it ...
9
votes
2answers
289 views

Menu item “Interrupt Evaluation…” missing in V10

The menu item “Interrupt Evaluation…” seems to have disappeared in Mathematica 10 on OS X. Well, this is a bummer. I personally use Mathematica for very long calculations, and I was using this ...
2
votes
1answer
78 views

Inactive derivative: extract constants

I have a problem with an unevaluated derivative. In the example code below, i need the integration wrt to y be evaluated, while the differentation wrt x needs to stay unevaluated. I see the point that ...
5
votes
3answers
282 views

difficulty abstracting the OptionValue pattern

I am building lots of functions that use Options and OptionValue and wanted to reduce the redundancy in the expressions that ...
0
votes
1answer
46 views

Ivar error with Fit inside Plot

I'm trying to plot this Plot[Fit[med,{1,x},x],{x,0,10}] Why this doesn't work? I find out that if I do ...
3
votes
5answers
218 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 ...
6
votes
1answer
287 views

Functional-Style Partial Application and the Accumulator Pattern?

Following up on Functional-style Fixed-Length Queue Object?, I want to generalize it to a functional-style accumulator pattern. Lots of things look like accumulators, loosely defined as binary ...
3
votes
2answers
125 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: ...
2
votes
1answer
110 views

How to explain the behavior of Rule inside these functions [duplicate]

I'm trying to define a function that takes an expression and spits out a pure function involving a replacement rule of that function's variable. An example would be a function ...
3
votes
1answer
529 views

kernel Local crashes during the course of a For loop

I want to find the minimum of the function r[x,p] subject to the constraint w[x,p,t]==0 (t ...
4
votes
1answer
194 views

Can $\it{every}$ usage of While be changed into NestWhile?

Ok, I think this problem is more close to philosophy. :P I've some idea now. But I'm not sure whether it's correct. For the purpose of convenience, I will use some C-like code instead of MMA's. A <...
3
votes
2answers
79 views

Mathematica automaticly evaluates some cells

Is there a command or a trick to tell Mathematica to not automaticly evaluate some cells? I use the NMinimize function to calculates some coordinates and then use ...
3
votes
0answers
174 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 ...
1
vote
0answers
73 views

Evaluation inside Compile

here's a simple question: I have a function: ...
6
votes
1answer
302 views

How to simplify expression and use HoldForm at the same time?

Hopefully a simple problem for the experts here. I have a need many times to build a symbolic expression for an equation (say a PDE) to use for plot labels in a low level function inside ...
6
votes
2answers
222 views

Why does Mathematica appear to change the head of certain expressions?

I don't know if the question trivial or not (if so I will delete it), but here is what I have: I know that x x (* x^2 *) Looking at the full form gives <...
0
votes
1answer
174 views

Simplifying a symbolic product of rational powers

I'm trying to symbolically evaluate a lot of equations that can consist of up to 10 parameters. The form of these expressions is a product/quotient of rational powers of the mentioned parameters, ...
0
votes
0answers
33 views

Expressions to functions, and evaluation [duplicate]

When calculating derivatives a expression is the result: in:= f[x_,y_]:= 1 + 2 x + 3 x^2 y + 4 x y^2 in:= D[f[x,y],x] out= 2 + 6 x y + 4 y^2 how do i make this ...
2
votes
2answers
86 views

Order of Evaluate for Map

I would like to get a list of variable names as strings. For example, x = 1; y = 2; Map[SymbolName, Unevaluated /@ Unevaluated@{x, y}] {"x", "y"} This works ...
5
votes
5answers
251 views

How to make a table of $\sum_{i=1}^n$?

I want to create a table of $\displaystyle \sum_{i=1}^n i^k$ for $1\le k\le 5$. The output I want to obtain is a TeXForm output as follows. \begin{align} \sum_{i=...
4
votes
1answer
133 views

Example from Mathematica documentation (ExtremeValueDistribution) seems to be evualting “forever”

I am referring to this example at the reference page for the extreme value distribution: http://reference.wolfram.com/mathematica/ref/ExtremeValueDistribution.html#6764486 The first three commands ...
4
votes
2answers
79 views

With command does not behave as expected according to its Attributes

The attributes of the With command are HoldAll which means it should not evaluate its arguments before its starts its business. ...
2
votes
0answers
53 views

Timing of ParallelDo versus Do: simple example [duplicate]

I'm trying to understand why a simple do-loop takes substantially longer when done in parallel than sequentially: ...
4
votes
1answer
164 views

ExampleData menu view

I'm trying to build an ExampleData browser, so that the "collection"/"type" is selectable in a drop down menu, and the "name" is selectable in another drop down menu. What I have so far: ...
9
votes
1answer
358 views

Performance of Dispatch and lists of Rules

The issue outlined here seems to be no longer present in version 10, if you use a Dispatch table! This because a Dispatch table ...
2
votes
2answers
131 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 ...
1
vote
2answers
271 views

How to get the absolute difference between two angles

I need a function that will give me the shortest separation between angles that range from -pi to pi. For example if I have two angles 3pi/4 and -3pi/4, I would like a function that will tell me pi/2 ...
2
votes
1answer
151 views

Generate conditions seems to not work [closed]

I am trying to compute the following integral Integrate[E^(I*k*Omega*t), {t,0,T}, GenerateConditions->True] for which Mathematica returns ...
8
votes
3answers
831 views

Why are functions called first-class objects in Mathematica?

I've heard lots of people say a function is a first-class object in Mathematica. "Everything is an expression, including function." "There is no distinction between functions and data." Having read ...
1
vote
0answers
82 views

How to implement nested With as a single construct using functional programming (Fold)?

It is possible to define my own With construct where each local constant can depend on the previous defined local constants? I wish to replace something like this ...
1
vote
1answer
367 views

FindRoot with vector functions

I'm trying to solve a system of non-linear equations with FindRoot, and I get the answer, but also a ...
0
votes
1answer
416 views

How does Mathematica interpret a expression?

I'm a beginner to Mathematica. I'd read several document. But I still have a problem. For example, every expression in Mathematica are of the form ...
4
votes
1answer
175 views

ParallelEvaluate: Evaluation Rules and Increment

I'm trying to understand how ParallelEvaluate works, considering the two following snippets: ...
1
vote
3answers
386 views

Automatically evaluate next cell

I am new to Mathematica. I am trying to achieve the following: I need one input cell in which I set parameters, then another input cell where functions are defined and calculations are performed. ...
3
votes
1answer
86 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 ...
4
votes
3answers
189 views

will the same result be evaluated twice per evaluation?

here is the silly question of mine, if mathematica takes 3 seconds to evaluate the function ...
1
vote
0answers
170 views

Expression for evaluating multiple functions?

I am constructing 3D data points for a plot and corresponding to specific conditions "manually". I define the values of five parameters [these I always have to define myself]. From those, I evaluate ...
0
votes
4answers
172 views

Minimization in single component of BSpline to extract points

I smoothed some data with a BSpline $B[t] = (x[t],y[t])$. I would like to extract certain points from this spline by their x-Values, $x_0$. The easiest way I came up with was to minimize $B[t][[1]]-...
2
votes
2answers
2k views

Integrating a Simple Piecewise Function

If I define f[x_]:=If[x<0,-1,1] and then integrate,say Integrate[f[x],{x,-3,7}] I get what I expect, namely 4. But ...
5
votes
3answers
3k views

How to force 2+2=5

I was looking at this question (writing a program such that 2 + 2 = 5) and tried to write something in Mathematica, but I couldn't get something to work without completely replacing ...
5
votes
2answers
134 views

ReplaceAll performance problem: packed arrays on the LHS are unpacked when the RHS is too long

The following is one of the most mysterious performance problems I encountered and came up while extending the booleval function mentioned here. I am looking for a ...
6
votes
1answer
258 views

Machine Epsilon

I'm trying to evaluate the machine epsilon of my computer (see below). I wrote this: ...
0
votes
0answers
57 views

Scoping problem with Manipulate [duplicate]

Consider the following simple code: f = Sin[a x]; Manipulate[ Plot[f, {x, 0, 10}], {a, 0, 10}] Manipulate takes f to be ...
3
votes
1answer
97 views

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

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 ...