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Questions tagged [pure-function]

Questions about implementing or applying functions which: (1) always yield the same result for the same input, (2) are independent of outside information, and (3) produce no side effects.

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425 views

Subtracting elements in a nested list

I have a list containing 500 rows, each of 37 elements; i.e., a 500 x 37 matrix. My goal is to substract in each row each element from the first. My approach in mind is to call each list by a ...
541 views

Combining # & pure functions with post-fix notation

I can't find the link anymore but there was a talk at a Wolfram conference (referencing v7 I think) where the authors highlight that stringing together functions like this: ...
134 views

Change the coordinates from $(x,y)$ to $(\mu,\theta)$?

Suppose I have the following definition: $$x=\cosh \mu\cos\theta, \quad y=\sinh\mu\sin\theta$$ I want to change the coordinates $(x,y)$ to $(\mu,\theta)$, suppose $x\in(-1,1), y\in(-1,1)$. Here ...
34 views

Bug with LinearRecurrence and Slot/SlotSequence?

The code below runs without error: LinearRecurrence[{##}, {1}, 5] Each term is the previous term squared times the index of the previous term. If the ...
36 views

How to deal with common arguments for several helper functions in a module?

Suppose a module exports functions like Calculate1[...,T], and Calculate2[...,T] which have several arguments in addition to <...
661 views

Writing lambda expressions in terms of pure functions

I am trying to create some functions that I want to comfortably compose together using the pure functions. The functions were originally written in $\lambda$-expressions so I would like to keep the ...
171 views

Making pure functions listable [closed]

I have a very large number of functions defined in the following manner: f = Function[{x}, x^2]; f = Function[{x}, x^3]; I would like to make all of these ...
136 views

Defining pure function using module

I am creating a function fun which takes a parameter p and returns a pure function: ...
474 views

Combining pure functions

Is there an easy way to combine pure functions into a single pure function? For example, say I have f = #1^2 &; g = #1 - 2 &; and I want to define a new ...
117 views

Vector of Pure Functions

I'm trying to make a function that takes in a vector of pure functions (representing a parametric equation) and returns another vector of pure functions representing an offset curve. Here's what I ...
149 views

Replace all the elements in a list at a given level with the level number

How can I change the function replace in a pure function way? replace[list_List, n_] := (g[a_] := n; Map[g, list, {n}]); I ...
134 views

How to pre-evaluate parts of a lambda or a delayed-assigned function?

I have an expression which I'd like to evaluate and use as a subexpression of a delayed-assigned expression. But I need it to be evaluated before actual assignment, while other parts of the full ...
82 views

function on parts of lists works only in pure function?

For example, I'd like to take the first four upper left values of a matrix, i.e. f[x_] := f[x] = x[[;; 2, ;; 2]]; This works nicely, e.g. ...
545 views

Creating a pure function that does operations with pure functions

Suppose I have two functions defined as follows: a = #+3& b = #^2 + 3& So when I call a and ...
87 views

Time-stepping an equation in Mathematica

I have an iterative integral equation of the form n(k,t+dt)=n(k,0)+dt\int_{0}^{\infty}dp\int_{0}^{\pi}d\alpha\int_{0}^{2\pi}d\beta\int_{0}^{\pi}da\,p^{2}q^{2}\sin(\alpha)\sin(a)\frac{(n(p,t)+1)}{\...
229 views

How to convert numbers to currency values?

I am trying to create a way to convert some values of numbers into currency (dollars). The example I display below takes in three random numbers between -4 and 4, and rounds them to the second decimal ...
133 views

How to produce this list of pure function pairs

I need to produce this ...
114 views

Bug when combining Dataset with a scoping construct and Map

The following fails in v11: ...
238 views

Is anonymous pure function a scoping construct?

In recent thread was raised the question: why anonymous pure functions Function[body] (or body &) do not rename symbols in ...
533 views

Using predefined expressions as free variables in a pure function [duplicate]

I want to have a function value of an expression where some variables are solutions to some set of equations, with some values of parameters. I had an idea to use pure functions for that. However, ...
325 views

Unexpected variable renaming depending on form of a pure function

I encountered unexpected difference in variable renaming behavior depending on whether a pure function with a named parameter, or a pure function with a slot is used: ...
808 views

Pure functions are not functions?

According to the manual: "HoldAll is an attribute which specifies that all arguments to a function are to be maintained in an unevaluated form." The following code yields, as expected, ...
37 views

How to use OptionValue inside a pure function [duplicate]

I want to define a function with OptionsPattern as argument which returns a pure function using OptionValue: ...
176 views

Optimization of the solution to an ODE

Apologies if this is obvious -- I'm very new to Mathematica. I'm trying to minimize the solution to an ODE with respect to a variable. The following code generates the solution to the ODE, ...
154 views

Evaluate pure function through round brackets

In have some matrices of pure functions or numbers which I multiply by other matrices or vectors. I would like the functions to be evaluated in the result, but all that I get is something like this: <...
502 views

Solving a pure function to obtain function definition and then map that function

I've been trying to use Solve with pure functions to receive function definition and then use it with Map , to obtain results from mapping function to some data. Here is an example ...
194 views

Automatic generation of pure function

My main problem consist in the creation of a sort function which wolud be used inside SortBy. Introduction The principle of the sort to apply is the following (...
2k views

Can you plot pure function without specifying variable?

Given a pure function, e.g. f=Sin[#]&, it is possible to plot it with introducing an arbitrary local variable, e.g., ...
88 views

Matching All Functions [duplicate]

Is there any way to match all functions? There's an existing answer for matching functions of one parameter (_@_) but it doesn't work for trying to test if a symbol ...
351 views

How to force evaluation inside the body of a pure function?

For example, I'm writing a function to scale my list of numbers into a specific range. It goes like ...
161 views

Select with test function that depends on # [duplicate]

I'm trying to teach myself to use pure functions and slots as much as possible. Here is my problem. I have a list: ...
349 views

How to use Select according to a list of criteria to produce a list of subsets of another list obeying those criteria [duplicate]

The code Print[Select[{1, 4, 3, 9}, Mod[#, 3] == 0 &]]; Print[Select[{1, 4, 3, 9}, Mod[#, 3] == 1 &]]; Print[Select[{1, 4, 3, 9}, Mod[#, 3] == 2 &]] ...
253 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 ...
125 views

Creating a list of unevaluated pure functions with Apply

Suppose I have a list list with length L and a function ...
58 views

Deciphering Coding Shortcuts [duplicate]

I'm having trouble deciphering why the following couple of expressions evaluate the way they do. #&@@ This returns the first value of a list. Why? Naïvely I ...
133 views

How to write this code as a pure function? [duplicate]

The code has three places with same variable ls. So I think it would be possible to write it as a pure function. ...
37 views

Why is g[#1, #2] & different from g[##] & for a function with two variables in this example? [duplicate]

If we only consider functions with two variables, I expect g[#1, #2] & is the same as g[##] &. But in the following ...
90 views

Translating syntax of a pure function

I have a matrix in complex exponential form. I want to factor out the complex exponential form and then express the inside in the a+i*b form. For example: \begin{bmatrix} e^{i \frac{\pi}{4}} ...
87 views

How to get the values out of Alternatitves? [closed]

Saying we have something like: SomeFunction[ ... { Alternatives[1, 2, 3] :> "something" } ... ] How can I know if ...
477 views

How can I create currying functions using pure function syntax?

For example how can I write In: pureFunctionSyntax[myF] /@ {7, 3} Out: {myF[7, Log], myF[3, Log]}
511 views

Why does #0[] &[] output 0?

When a pure function accesses the first element of itself, 0 is output. What is the logic behind this, or is there any?
85 views

How to use pattern matching to apply a function to specific elements of a matrix

I have a 3x3 matrix testweightedgraph = {{{}, {p, q, pq, pq}, {}}, {{p, q, pq, pq}, {q}, {}}, {{}, {}, {}}}; whose elements are (possibly empty) lists. I would ...
146 views

Replace variable with # and pass function body as an argument to a function

I have a very simple problem, which I would like to make a bit general, but none of my naive approaches have worked yet. This is what I want to do step by step: Define a parameter: ...
1k views

Is it possible to reference “self” from a pure function?

This would calculate the factorial of 6, if the "self" was the function itself. Is there something that could allow this? ...
1k views

“Nonatomic expression” error when identifying certain positions in a list [duplicate]

Please can anyone help ? I have a list of sets, and I am trying to find the positions in that list of those sets which are subsets of a given set. (Here I am ignoring the distinction between lists and ...
177 views

Working with functionals [closed]

I am trying to work with functionals in Mathematica, this means that I want to define a function of a function. I defined my function of a function as: ...
1k views

Cases vs Select, Pattern vs Pure function [duplicate]

What is the difference between having Cases with selection condition presented by pattern and a with pure function as condition? ...
243 views

Substitute a function's definition for its name

I'm having trouble with a function which is supposed to work on another function. Simplified version: ...