# Tagged Questions

Questions about Mathematica's functional programming style, including the use of pure functions (Function[], #, &) and functions such as Map, Apply, Nest, and Through.

198 views

### Transforming a list of the form {{{x, y}, z}, … } into the form {{x, y, z}, … } [duplicate]

This should be a fairly simple question, but I can't figure out how to do it. I have a list of points of the following form: ...
180 views

### Alternatives to For/Do Loop to optimize indexing Matrix

I am trying to optimize my code that searches for elements in the rows of matrix that are greater than 0. Then use that position to grab the element from other matrix. I use the do loop to iterate ...
21 views

### Express anonymous with formal parameters [duplicate]

I'd like to express the function F = Function[{#2[[1]] + #1[[2]]/#1[[1]], #2[[2]] + 1/#1[[1]]}] using explicit formal parameters. I've tried ...
2k views

### Scan vs. Map vs. Apply

I cannot understand the difference between Apply, Scan, and Map. I have tried to play with ...
462 views

### Gâteaux (directional) derivatives and higher order differentials of a functional

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

### Define inverse Laplace operator as map from functions to functions

I am trying to implement the inverse Laplace operator through P[g_] := h /.NDSolve[{h''[x] == g[x], h[0] == 0, h[1] == 0}, h, {x, 0, 1}][[1]] If I now define ...
502 views

### Does Mathematica have a functional programming idiom to loop over a list till a condition is met? [duplicate]

The module below takes a list of integers and performs fadic addition on it (if a bit slowly). ...
35 views

### Which the functions of parameters can use Span [closed]

As I know,ImageValue,PixelValue,ReplaceImageValue,...
43 views

### How to round all the numbers in a function?

I have a complicated function that is a combination of floating-point numbers and variables. I want all the numbers rounded off, but I have no clue how to do this. For example I would want ...
179 views

### How to construct the RHS of Wick's theorem

I've been trying this for a few days now, but I just can't seem to find an efficient (speed-wise) functional way to code the following task. Context: I would like to construct an expressions that is ...
174 views

### Core functions or operations that every aspiring Mathematica programmer should know? [duplicate]

I am aware that there are common yet very powerful operations like Map, Thread, Apply, ...
308 views

There seem to be lots of papers discussing the functional programming paradigm terminology for Haskell, such as monad, category theory, lambda calculus, *morphism, etc. People study concepts and ...
50 views

### Different ways to program a recursive algorithm

Construct f (a numeric function) which takes multiple arguments with the following property: The single argument case $f(x_1)$ is meaningless, and the two-argument ...
179 views

### The usage of MapIndexed, can it be removed?

project euler 67 When I'm solving this problem, my solution is as following. You can download the data file there. ...
5k views

### General strategies to write big code in Mathematica?

I think after six months of exposure to Mathematica and the Wolfram Language I am fairly OK with writing short codes and snippets. However, what are some general strategies to use in order to write ...
86 views

### Partial Function Evaluation [closed]

How can I evaluate only part of a stack of function calls? In particular, given f[x_,y_,z_]=x+y+z;, say, I'd like to define a function ...
55 views

### Strange sharp spikes causing overflow while doing gradient descent

I am trying to find a function h(r) that minimises a functional H(h) by gradient descent. The result of H(h) is a single number. (Basically, I have a field configuration in space and I am trying to ...
65 views

### How to use currying to write a tail recursive function for summing factorials given a certain bound

I am very confused about how can i use currying to write a tail recursive function for summing factorials within a certain bound or summing the bounds i.e. given [1,5] i should be getting 1!+2!+3!+4!+...
62 views

### Pairing values with their indexes for MapThread

Several operations require you to map over a list of values and to know the index of each value as you process it. To accomplish this, my current somewhat ugly solution uses MapThread: ...
745 views

### What's the most “functional” way to do Cholesky decomposition?

I can do Cholesky in a procedural style, such as: ...
825 views

### What's the cleanest functional-programming style way to perform this list operation?

I am looking for the correct method for accomplishing the unknown piece in the following code snippet: rolls = Tuples[Range[1, 4], {2}] ...
103 views

### Counting runs in bits, along with their starts and lengths, in functional style

Here is some code to visualize Project Euler Problem 502. The code scans for runs of bits in the binary representation of an integer, and outputs the beginning position of each run and the length of ...
446 views

### How to keep some of the results of the NestList

I'm using some iterative arithmetics to calculate wave propagation with the help of NestList. I have to use a small step size for iteration to guarantee the accuracy, which lead to too much data (e.g, ...
71 views

### RealDigits and functional style

So while thinking about Replacing numbers of which you only know certain digits I have faced, again, a problem that I find hard to extract from RealDigits' output ...
132 views

### Variable naming conventions for nested pure functions [closed]

My understanding is that for nesting pure functions, one should use the explicit version of pure functions. I would like to know the best way of making it readable for people. I currently have ...
50 views

### Recognition Power Head for numeric value

We know: Map[Head, {a, a^2, a^3}] (* {Symbol, Power, Power} *) and Map[Head, {2, 2^2, 2^3}] all of them will be known as <...
117 views

### how to map a function on a variable list

The following is just an example that captures what I want to do (more on it at the bottom). I'm trying to do something that can be paraphrased as follows: I have a global list, say ...
171 views

### How best to simulate n-body systems in a functional way

I want to simulate a N-body system in the most functional way possible. The system I'm modeling are metallic colloidal particles in a solution of peroxide water, as here http://arxiv.org/pdf/1502....
121 views

### The basic primitive recursive functions

How can the basic primitive recursive functions be expressed in the Wolfram Language? Apparently here's an example for primitive recursion: ...
142 views

### How can I do a two dimensional Fold? [closed]

I'd like to Fold over higher dimensional objects than lists. Semantically, the format would be something like ...
1k views

### Better code to find Narcissistic number

My code finding Narcissistic numbers is not that slow, but it's not in functional style and lacks flexibility: if $n \neq 7$, I have to rewrite my code. Could you give some good advice? ...
2k views

### Using pure functions in Table

I need a table with the elements made of pure functions and list elements. This is a simplified example: I need a list as: ...
278 views

### How to get “Signature” of each element of “Permutation” output

I need to sum over all possible permutations, multiplied by the Signature of each permutation of a given list of symbols. But, I don't know how to determine the <...
254 views

### MapAt and generic Functions on Associations and Datasets

These are distinct but related questions about mapping functions to Associations and Datasets. Given: assoc = <| a -> 1, b -> 2, c -> 3|> And <...
926 views

### How can I avoid using a For-loop in my code?

I am trying to avoid using For because I heard that For is not cool in functional programming. Below is a problem that the first ...
86 views

### Delimited Continuations: Easy? or Fundamentally Difficult?

Apologies in advance for the length of this question, but this is as short as I have been able to make it. The Prescription I'm looking at the following tutorial on delimited (or composable) ...
94 views

### How to organize expression by symbols (like Collect), but apply different functions to each coefficient

I want to mimic the functionality of Collect[expr, {vars}, func], but with the following modification: The function f that is ...
3k views

### Functional style using lazy lists?

Let's say I want to answer the question "what are the first 400 palindromic prime numbers?" The first approach that comes to my mind from the set of languages that I know is to use some sort of lazy ...
290 views

### Handy / flexible directory tree operations

Is there any shorter / more handy / more flexible way to get directory tree as a nested Rules/Associations list? I tried to incorporate ...
74 views

### Defining a list of functions

I'm using polynomial mappings such as s[{x_,y_}] := {x + y^2, y -x} and playing with compositions of such mapping, e.g. ...
105 views

I have data ...
102 views

### Repeatedly apply a bivariate function with one argument running over a list

I'd like to know how, given symbols f and g, and a list {a,b,c,...}, to produce the ...
46 views

### Deciding whether the return value of a function is defined based on its input [duplicate]

I have been met with the following problem: I have defined the following: myFunc[e_Integer]; That means, if I call: ...
97 views

### Iterations in Mathematica [closed]

this is probably a very easy question for all of you. I have a stochastic Mathematica code (not important what it's exactly) which gives me a number at the end. Now I want Mathematica to run this ...
204 views

### How to terminate early a functional computation

Problem description: Given a list $A=\{1,2,0,7,0,-1,2,6,\ldots\}$ and a list $B=\{0,7,0\}$ write a program that determines whether $B$ appears in $A$ or not. Note: the order of $B$'s items does matter....
117 views

### A better way than using nested For-loops to make a search list

I'm generating a List that can be up to 26 values long, a simplified example is below. Is there a better way than nested loops? ...
129 views

### Writing code which generates a function to append many columns to a dataset

I love datasets in Mathematica. Say I have one that looks like this: ...
74 views

### How can I get all pairs of values from an association with elements key->list

I have an association of the form ds=<|key1 -> list1, key2 -> list2,... ,keyn -> listn|> I would like a simple way to map a function to all pairs <...