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

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3
votes
5answers
100 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
81 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 ...
2
votes
0answers
44 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
2answers
76 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: ...
0
votes
3answers
134 views

Avoid creation of OwnValues when inserting transformation rules into Experimental`OptimizeExpression

I have a large list of transformation rules that I want to simplify. I find Experimental`OptimizeExpression works as it gets me the answers. My question is: **I can only get this to work when I ...
2
votes
1answer
92 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 ...
2
votes
1answer
74 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 ...
2
votes
1answer
92 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 ...
0
votes
0answers
72 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
2answers
48 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 ...
0
votes
0answers
38 views

Evaluation inside Compile

here's a simple question: I have a function: ...
6
votes
2answers
174 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 ...
1
vote
2answers
97 views

Higher derivative [closed]

Is there more efficient way to rewrite this code in order to compute 2nd and higher derivatives of r=sqr{x^2+y^2+(z-a)^2}? ...
0
votes
1answer
47 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
31 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
51 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 ...
14
votes
4answers
463 views

HoldForm doesn't hold form

In Mathematica version 10, HoldForm no longer produces the same results as in version 8 (edit: I only have versions 10 and 8 installed, so can't compare to version ...
9
votes
3answers
117 views

Implement settable properties

I am looking for advice on implementing the following. (It is possible that the answer is that it is simply not a good idea to do this.) I would like to have an object similar to ...
10
votes
2answers
203 views

Why doesn't a Composition[] hold its arguments and what can be done about it?

Now that Composition (also RightComposition) has shorthand syntax I am more inclined to use it, however what I feel should be ...
3
votes
1answer
86 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: ...
1
vote
2answers
153 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 ...
8
votes
3answers
595 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 ...
3
votes
1answer
127 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: $L(u(x))=\int_0^1 \frac{1}{2} (u'(x))^2 dx$ ...
1
vote
0answers
69 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
85 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 ...
-3
votes
1answer
76 views

Why does the function Evaluate speed up one function by orders of magnitude and another function not at all?

I've got two functions, one sample function (function 1) i've created for demonstartion purposes here, and my actual function. The function Evaluate speeds up the sample function by orders of ...
0
votes
1answer
106 views

Why does Evaluate fail? [closed]

If i use this code: ...
1
vote
1answer
74 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
113 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 ...
2
votes
0answers
42 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: ...
2
votes
1answer
78 views

ParallelEvaluate: Evaluation Rules and Increment

I'm trying to understand how ParallelEvaluate works, considering the two following snippets: ...
0
votes
3answers
65 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
53 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 ...
2
votes
3answers
164 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
59 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
1answer
43 views

Resolving Error: Mathematica evaluation order on Lists

I have a table that is 27 x 27, each entry corresponds to an element from the periodic table. I use the replacement rules in element list to allow me to convert a list of elements into a list of ...
0
votes
4answers
142 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 ...
1
vote
2answers
49 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 ...
4
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 ...
6
votes
1answer
103 views

Machine Epsilon

I'm trying to evaluate the machine epsilon of my computer (see below). I wrote this: ...
5
votes
2answers
84 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 ...
0
votes
0answers
38 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
82 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 ...
8
votes
2answers
155 views

How to correct this, `f[a_] := FindRoot[eq == 0, {x, 0.5}]`, where `eq` contains a parameter $a$, without using `eq[a]`?

I want to solve an equation with a parameter $a$, and define the result as a function of $a$. It is something like this: ...
6
votes
1answer
112 views

Can Mathematica do two evaluations at the same time?

When one evaluation is running, if I want do another evaluation, Mathematica will put the second one in the queue and run it after the first evaluation finish. However, the first evaluation may take ...
3
votes
1answer
44 views

Apply a function to the current selection in place

Say a have the function foo: foo[x_] := x + 2 Like the Evalution ...
10
votes
2answers
345 views

How do I get Mathematica to return a function call unevaluated?

How do I get Mathematica to return a function call (conditionally) unevaluated? I expect this may use the slightly-mysterious Hold function. As a toy example, ...
0
votes
2answers
70 views

Simplifying Fourier transform of a complicated function

I would like to evaluate the following expression but takes too much time. I would be greatly appreciate for any comments to make it fast. ...
1
vote
0answers
38 views

can I evaluate multiple cells at the same time? [duplicate]

my laptop has 2 cores, can I assign a core to evaluate one code, and the other core for another code in parallel instead of evaluating in sequence? thanks
0
votes
1answer
49 views

Optimizing repeated function calls

Easiest way to keep my library nice, is to naively call some functions many times with same parameters. Doing so prevents from zoo of (library-)global variables and complicated initialisation ...