Questions tagged [lazy-computations]

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116
votes
1answer
7k views

File-backed lists/variables for handling large data

Background Currently I am working with some large data (most of it generated by Mathematica itself). I usually find it a hassle to do this. For example, I just exported a large amount of data to ...
109
votes
9answers
5k 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 ...
23
votes
7answers
2k views

Permutations[Range[12]] produces an error instead of a list

This input: Permutations[Range[12]] Results in this (error) output: ...
20
votes
1answer
1k views

Lazy lists of Tuples and Subsets

I'm trying to build a lazy list that evaluates the n'th m-tuple or subset of a given list using Mathematicas ordering without calculating all the Tuples. The purpose is to allow for example the ...
35
votes
2answers
3k views

Is there a built-in equivalent to Python's enumerate?

Python's built-in function enumerate takes an iterable over $(a_0, a_1, \dots )$ as argument and returns an iterable over the sequence of pairs $((0, a_0), (1, a_1),...
13
votes
4answers
588 views

Lazy form of Tuples/Outer to loop over list of lists

This is less a question and more asking if someone has implemented this already, with more skill. I need to perform the Outer-like generalized outer product of a ...
10
votes
1answer
897 views

Alternative to Subsets to generate k-combinations

I need to generare a huge number of k-combinations for a quite big set of numbers (more than 100), so I would avoid Subsets because it requires too much memory (it generates all subsets at once). I ...
33
votes
1answer
981 views

Efficient lazy weak compositions

In Mathematica all weak k-compositions of integer n can be generated using permutations of integer partitions: ...
19
votes
1answer
320 views

How to use Streaming package in v11.1?

I am trying to use the streaming package for lazy list operations demonstrated in this post. But I found that the package was significantly changed in version 11. After some observations, I found that ...
18
votes
7answers
2k views

How to map and sum a list fast?

The following takes a lot of memory and is slow: AbsoluteTiming[Total[Map[#^2 &, Range[1, 100000000]]]] I suspect this is because it first calculates and ...