Communities

Writing
Writing
Codidact Meta
Codidact Meta
The Great Outdoors
The Great Outdoors
Photography & Video
Photography & Video
Scientific Speculation
Scientific Speculation
Cooking
Cooking
Electrical Engineering
Electrical Engineering
Judaism
Judaism
Languages & Linguistics
Languages & Linguistics
Software Development
Software Development
Mathematics
Mathematics
Christianity
Christianity
Code Golf
Code Golf
Music
Music
Physics
Physics
Linux Systems
Linux Systems
Power Users
Power Users
Tabletop RPGs
Tabletop RPGs
Community Proposals
Community Proposals
tag:snake search within a tag
answers:0 unanswered questions
user:xxxx search by author id
score:0.5 posts with 0.5+ score
"snake oil" exact phrase
votes:4 posts with 4+ votes
created:<1w created < 1 week ago
post_type:xxxx type of post
Search help
Notifications
Mark all as read See all your notifications »
Sandbox

Comments on Reduce over the range [1..n] [FINALIZED]

Post

Reduce over the range [1..n] [FINALIZED]

+7
−0

Task

I often need to find the factorial of a number or the sum of all numbers up to a number when cheating on math tests. To help me with this, your task is to write $F$, a generalized version of those functions:

$$F(n) = 1 * 2 * \space ... \space * (n-1) * n$$

Please note that the operator $ * $ does not necessarily represent multiplication here, but stands for a commutative, associative operator that will be an input to your program/function. This means that $a * b$ is the same as $b * a$, and $a * (b * c)$ is the same as $(a * b) * c$. Its inputs are positive integers, and its outputs are integers.

Rules

  • $n$ will be a positive integer.
  • $*$ is a binary function/operator that can be taken in any convenient format, including but not limited to:
    • A function object
    • A function pointer
    • An object with a method with a specific name (e.g. Java's BiFunction)
    • A string that can be evaluated to get a function
  • $*$ is a blackbox function. That means that you will not be able to examine it to see how it works; all you can do is feed it two positive integers and get an integer back.
  • The output of your function will be an integer (not necessarily positive).
  • This is code golf, so shortest code in bytes wins!

Testcases

f         | n  | F(f, n)
Add       | 1  | 1
Add       | 5  | 15
Multiply  | 1  | 1
Multiply  | 5  | 120
XOR       | 1  | 1
XOR       | 2  | 3
XOR       | 5  | 1
XOR       | 10 | 11

Questions:

  • Interesting enough? Is a vanilla factorial better?
  • Are the tags okay?
  • Needs more testcases?
  • Input rules okay?
History
Why does this post require attention from curators or moderators?
You might want to add some details to your flag.

2 comment threads

Regarding XOR (3 comments)
General (6 comments)
Regarding XOR
General Sebast1an‭ wrote over 3 years ago

I have no idea how you got those XOR values. It's kinda confusing what values are going in.

user‭ wrote over 3 years ago

I don't understand what's confusing you about them, but perhaps this worksheet will help.

General Sebast1an‭ wrote over 3 years ago

user‭ Nevermind, I figured it out. It's in my answer already.