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.

learn more… | top users | synonyms

1
vote
1answer
47 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: ...
1
vote
2answers
338 views

Solving pure functions

I've been trying to use Solve with pure functions to receive function efinition and then use it with Map , to obtain results from mapping function to some data. Here is example ...
4
votes
2answers
140 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 ...
15
votes
4answers
905 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., ...
1
vote
0answers
78 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 ...
1
vote
1answer
60 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 ...
6
votes
1answer
108 views

Select with test function that depends on #

I'm trying to teach myself to use pure functions and slots as much as possible. Here is my problem. I have a list: ...
0
votes
4answers
100 views

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

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 &]] ...
0
votes
2answers
455 views

Expansion in Basis Functions

I am trying to create an expansion of the form f[x,y]->Sum[Cn[x] y^n,{n,1,order}] To replace the function f by the ...
25
votes
2answers
1k views

Is there any way to define pure functions with optional arguments?

For example consider the following function: Function[{u,v},u^2+v^4] Is there anyway to define default values for the variables ...
1
vote
0answers
117 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 ...
4
votes
1answer
81 views
0
votes
1answer
44 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 ...
22
votes
1answer
960 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? ...
1
vote
1answer
97 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. ...
1
vote
0answers
83 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 ...
1
vote
0answers
33 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 ...
0
votes
1answer
96 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: ...
0
votes
0answers
53 views

What makes items with head `Function` different?

I apologize beforehand for the muddleheadedness of this question. It reflects the fact that I'm trying to interpret outward "behaviors" of Mathematica expressions without having any understanding of ...
1
vote
2answers
65 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}} ...
6
votes
3answers
312 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[7]], myF[3, Log[3]]}
4
votes
1answer
296 views

Why does #0[[1]] &[] 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?
3
votes
3answers
53 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 ...
1
vote
2answers
36 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 ...
0
votes
1answer
76 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: ...
0
votes
4answers
172 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? ...
8
votes
1answer
307 views

Mma10 mystery: Failure of pure function substitution with Interpretation?

Bug introduced in 10.0.0 and fixed in 10.0.1 I had code to display with subscripts from Displaying index as subscript on output: e.g. C[i] -> C_i with Notation[...] or Interpretation[..]? which ...
15
votes
2answers
1k views

What happens when you divide by ##?

I've been playing around with sequences a bit. In particular with using ## with unary and binary operators. Let's start simple, the following all make some kind of ...
4
votes
1answer
117 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: ...
1
vote
1answer
79 views

Pure “Select” function over matrix

I have several lists of tuples in the following shape: l1 = {{1, 134}, {2, 314}, {3, 164}} I do want to select, from each list, list elements fulfilling a ...
4
votes
5answers
164 views

Using Through with SlotSequence

I have an expression consisting of a few pure functions added together like so: f+g+h I want to add the bodies of these functions together and make that a pure ...
2
votes
1answer
121 views

Use Map with multiple arguments over a nested list

I noticed there are a few similar questions to mine on here, but I couldn't figure out how to accomplish this mapping. I have sets of data I want to plot, which represent intensity and frames, and I ...
7
votes
5answers
267 views

How to write an operator that acts on pure function (to give another pure function)

I would like to write an operator oper that acts on a pure function f with an undetermined number of arguments, with the syntax ...
0
votes
1answer
81 views

Pure Function that adds all arguments

the question asks to create a pure function that adds any number of arguments. Is the following acceptable? sum := Plus[##] & It does work, but can it be considered a pure function? I felt like ...
1
vote
1answer
61 views

Sum of Integers with a Pure Function

How would I find the sum of an argument, with the constraint that they are all integers (so if the argument contains a non-integer value, the function will not evaluate). I came up with these two: ...
1
vote
1answer
72 views

How-to implement iteration over a result of an iteration in a functional way

I have a pure function f:= #1 * #2 * #3 &; Which I can invoke in a following way: f[#,2,3]& /@ {1,2,3} Which ...
39
votes
2answers
2k views

Memoization with pure functions?

Is this possible? If I have a simple function, say: f=If[#>0,1,2]& then for each value of # this will re-evaluate f right? Is it possible to define a ...
17
votes
2answers
496 views

Using several anonymous functions mixed together

This works: list // BarChart[#[[2]], ChartLabels -> DateString @@@ #[[1]], ChartStyle -> "Pastel"] & This doesn't: ...
0
votes
0answers
70 views

Interpreting Mathematica output or producing cleaner output

Could someone please explain what the following would look like in standard math notation (or explain to me what this means): ...
4
votes
0answers
50 views

Wrong autogenerated package from notebook containing #key and Part as subscript

Bug introduced in 10.0.0 and persisting through 10.1.0 or later Mathematica v10.1.0, under Windows 8.1 x64 Mathematica v10.0.2, under Windows 1) Define a function in an initialization cell: ...
2
votes
1answer
79 views

Expressing a definite integral as pure function with the upper-bound as it argument

Suppose i have an integral which has a closed form, $\quad \quad \int_{a}^{b} f(x) dx=F(a,b)$ I want to use output function $F$ as a pure function, like ...
2
votes
1answer
90 views

Use of parenthesis and pure function

I had read that when using a pure-function it was a good general practice to enclose the function and the associated ampersand in parenthesis. (#^2 &)[a] I ...
27
votes
2answers
2k views

What are the cool kids talking about when they use ##&[]? [duplicate]

All the cool kids are apparently using ##&[] for Unevaluated @ Sequence[] but I have no idea what either means. ...
4
votes
2answers
115 views

Conflict with variables in pure functions

Consider the following snippet of code. Clear[f, g] f[x_] := Function[{i}, x]; g[h_] := Module[{Z}, Z[i_] := Print[h]; Print[h]; Z[1]; ]; When ...
0
votes
0answers
47 views

Having trouble reading this output (pure functions) [duplicate]

I'm after decoupling some odes and trying to solve them using mathematica but my output is in terms of Functions and InverseFuntions and I'm afraid I have no idea how to translate the output into ...
9
votes
2answers
703 views

How to programmatically covert a function-like rule to a pure function?

Is there a programmatic way to convert a Mathematica rule that acts like a typical mathematical function of one variable into the equivalent pure function? For example, the code should convert ...
1
vote
0answers
85 views

Using Solve without introducing extra variables

First post here. I've tried searching for an answer for this for a few days now, but it seems the search terms (solve, slot, etc) are too generic to be helpful. I'm struggling with understanding how ...
2
votes
1answer
100 views

Patterns for destructuring “Function” function arguments

I want to define a function for finding a Jacobian matrix of pure vector function of vector argument. I try ...
2
votes
3answers
208 views

How to make a symbolic vector into a pure function?

As part of a set of functions to implement a steepest descent algorithm I created my own n dimensional gradient function. It is defined as follows: ...