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

learn more… | top users | synonyms

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: ...
3
votes
3answers
210 views

How to make a defined symbol stay in symbol form?

How to make a defined symbol stay in symbol form? w = 3; g = 4; {w, g}[[2]] 3 I want the output to be ...
3
votes
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 ...
3
votes
2answers
68 views

Evaluation control with TagSet

Suppose I have a property associated with two functions using TagSet: ...
3
votes
3answers
134 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
195 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
votes
1answer
394 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
99 views

Fast evaluation of a function in many points

I need to feed to an external program a number of points (in Complex128 format) generated from the numerical evaluation of some function, e.g. $e^{i ...
3
votes
2answers
316 views

Expectation of a family of random variables

I did some search here, but seems that no one asked about this. I want to define a family of independent and identically distributed random variables, $x_1,...,x_n$, and then calculates the expected ...
3
votes
1answer
343 views

Manipulate executes expressions multiple times

I am using Manipulate for a rather intricate front end for data visualization. I was getting very sluggish performance and was able to boil the problem down to a ...
3
votes
2answers
52 views

How to avoid 0 OverVector[F] to be evaluated as 0?

I am fairly new in Mathematica and I am trying to work with scalars and vectors. I decided to denote vectors using OverVector (as example, ...
3
votes
1answer
85 views

Why doesn't my expression evaluate at the subkernel?

Consider this code: ...
3
votes
1answer
425 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
96 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 ...
3
votes
2answers
177 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
164 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
101 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
120 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
123 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
92 views

Map works but Thread doesn't

This question may be trivial, but I can't get past it for the life of me. I have $n$ matrices of dimension $p_i \times N_i$, with $i$ indexing the $n$-set. I also have $n$ vectors of the appropriate ...
3
votes
1answer
60 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 ...
3
votes
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 ...
3
votes
1answer
120 views

Strange integration

Bug introduced in 9.0 or earlier and fixed in 10.1 Note: Beginning with V10.1, this integral returns unevaluated but without error messages. I tried to evaluate this line ...
3
votes
1answer
81 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
votes
1answer
141 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
179 views

Evaluate in Plot leads to function error

Please help - I'm really struggling to understand why this evaluates with errors. ...
3
votes
1answer
534 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
1answer
318 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
41 views

Difference between Initialization Cell and Group

Is there a difference between setting a Cell or a Group of cells to be an ...
3
votes
1answer
50 views

An issue regarding the use of CopyToClipboard with dynamic content

Please, consider the following code: ...
3
votes
4answers
99 views

Working with ScheduledTasks inside DynamicModules

I have a question - is it possible to run ScheduleTask[] inside DynamicModule[]? What I have tried so far: ...
3
votes
1answer
328 views

Expanding huge expressions that simplify and factor

The following is for Mathematica 8.0.4 running on Windows 7 laptop (6GB memory). I have eight expressions that are unexpanded multivariate polynomials in 6 variables. They are huge expressions, so ...
3
votes
1answer
71 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
486 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 ...
3
votes
1answer
1k views

Why does Mathematica evaluate Sin[2.0] but not Sin[2]?

I can't understand why is it that In[88]:= Sin[2] Out[88]= Sin[2] while In[89]:= Sin[2.0] Out[89]= 0.909297 I even tried ...
3
votes
2answers
179 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 ...
3
votes
1answer
104 views

Some _atomic elements' TreeForm looks confusing with Level in appearance

In[1]:= Level[1/2,{-1}] Out[1]= {1/2} TreeForm[1/2] ...
3
votes
2answers
66 views

Simplify with assumption of unknown function [duplicate]

I have an unknown multivariate function entry[x,y,z], which is positive. Then how to get FALSE and entry[1,2,3] in the following evaluations? ...
3
votes
2answers
77 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
1answer
758 views

Order of operations, precedence in Mathematica [duplicate]

I get confused in the order of operations in Mathematica. For example, f /@ 10^{1, 2, 3} {10, 100, 1000} In my head, that ...
3
votes
0answers
84 views
3
votes
0answers
70 views

Is there an analogue of Evaluated->False (in FindRoot) for FindMinimum?

I guess functions like FindRoot, FindMinimum, etc puts the estimation number into the expression, and then do other ...
3
votes
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
0answers
88 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
1k views

Is there a way to stop evaluation immediately?

Sometimes I'll have a loop that I accidentally made too big. I'll evaluate, and MM will try to run through the entire loop. The program itself doesn't actually seem frozen... I can go to Evaluation-> ...
3
votes
0answers
113 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 ...
3
votes
0answers
519 views

A is fast, B is fast, but together they're Mathematica-crashing slow?

I'm trying to do something with finding solutions to a quantum mechanics problem with n wells. If there are 40 wells, I need to find the solution to an equation in the form: ...